1=head1 NAME 2 3perl561delta - what's new for perl v5.6.x 4 5=head1 DESCRIPTION 6 7This document describes differences between the 5.005 release and the 5.6.1 8release. 9 10=head1 Summary of changes between 5.6.0 and 5.6.1 11 12This section contains a summary of the changes between the 5.6.0 release 13and the 5.6.1 release. More details about the changes mentioned here 14may be found in the F<Changes> files that accompany the Perl source 15distribution. See L<perlhack> for pointers to online resources where you 16can inspect the individual patches described by these changes. 17 18=head2 Security Issues 19 20suidperl will not run /bin/mail anymore, because some platforms have 21a /bin/mail that is vulnerable to buffer overflow attacks. 22 23Note that suidperl is neither built nor installed by default in 24any recent version of perl. Use of suidperl is highly discouraged. 25If you think you need it, try alternatives such as sudo first. 26See http://www.courtesan.com/sudo/ . 27 28=head2 Core bug fixes 29 30This is not an exhaustive list. It is intended to cover only the 31significant user-visible changes. 32 33=over 34 35=item C<UNIVERSAL::isa()> 36 37A bug in the caching mechanism used by C<UNIVERSAL::isa()> that affected 38base.pm has been fixed. The bug has existed since the 5.005 releases, 39but wasn't tickled by base.pm in those releases. 40 41=item Memory leaks 42 43Various cases of memory leaks and attempts to access uninitialized memory 44have been cured. See L</"Known Problems"> below for further issues. 45 46=item Numeric conversions 47 48Numeric conversions did not recognize changes in the string value 49properly in certain circumstances. 50 51In other situations, large unsigned numbers (those above 2**31) could 52sometimes lose their unsignedness, causing bogus results in arithmetic 53operations. 54 55Integer modulus on large unsigned integers sometimes returned 56incorrect values. 57 58Perl 5.6.0 generated "not a number" warnings on certain conversions where 59previous versions didn't. 60 61These problems have all been rectified. 62 63Infinity is now recognized as a number. 64 65=item qw(a\\b) 66 67In Perl 5.6.0, qw(a\\b) produced a string with two backslashes instead 68of one, in a departure from the behavior in previous versions. The 69older behavior has been reinstated. 70 71=item caller() 72 73caller() could cause core dumps in certain situations. Carp was sometimes 74affected by this problem. 75 76=item Bugs in regular expressions 77 78Pattern matches on overloaded values are now handled correctly. 79 80Perl 5.6.0 parsed m/\x{ab}/ incorrectly, leading to spurious warnings. 81This has been corrected. 82 83The RE engine found in Perl 5.6.0 accidentally pessimised certain kinds 84of simple pattern matches. These are now handled better. 85 86Regular expression debug output (whether through C<use re 'debug'> 87or via C<-Dr>) now looks better. 88 89Multi-line matches like C<"a\nxb\n" =~ /(?!\A)x/m> were flawed. The 90bug has been fixed. 91 92Use of $& could trigger a core dump under some situations. This 93is now avoided. 94 95Match variables $1 et al., weren't being unset when a pattern match 96was backtracking, and the anomaly showed up inside C</...(?{ ... }).../> 97etc. These variables are now tracked correctly. 98 99pos() did not return the correct value within s///ge in earlier 100versions. This is now handled correctly. 101 102=item "slurp" mode 103 104readline() on files opened in "slurp" mode could return an extra "" at 105the end in certain situations. This has been corrected. 106 107=item Autovivification of symbolic references to special variables 108 109Autovivification of symbolic references of special variables described 110in L<perlvar> (as in C<${$num}>) was accidentally disabled. This works 111again now. 112 113=item Lexical warnings 114 115Lexical warnings now propagate correctly into C<eval "...">. 116 117C<use warnings qw(FATAL all)> did not work as intended. This has been 118corrected. 119 120Lexical warnings could leak into other scopes in some situations. 121This is now fixed. 122 123warnings::enabled() now reports the state of $^W correctly if the caller 124isn't using lexical warnings. 125 126=item Spurious warnings and errors 127 128Perl 5.6.0 could emit spurious warnings about redefinition of dl_error() 129when statically building extensions into perl. This has been corrected. 130 131"our" variables could result in bogus "Variable will not stay shared" 132warnings. This is now fixed. 133 134"our" variables of the same name declared in two sibling blocks 135resulted in bogus warnings about "redeclaration" of the variables. 136The problem has been corrected. 137 138=item glob() 139 140Compatibility of the builtin glob() with old csh-based glob has been 141improved with the addition of GLOB_ALPHASORT option. See C<File::Glob>. 142 143File::Glob::glob() has been renamed to File::Glob::bsd_glob() 144because the name clashes with the builtin glob(). The older 145name is still available for compatibility, but is deprecated. 146 147Spurious syntax errors generated in certain situations, when glob() 148caused File::Glob to be loaded for the first time, have been fixed. 149 150=item Tainting 151 152Some cases of inconsistent taint propagation (such as within hash 153values) have been fixed. 154 155The tainting behavior of sprintf() has been rationalized. It does 156not taint the result of floating point formats anymore, making the 157behavior consistent with that of string interpolation. 158 159=item sort() 160 161Arguments to sort() weren't being provided the right wantarray() context. 162The comparison block is now run in scalar context, and the arguments to 163be sorted are always provided list context. 164 165sort() is also fully reentrant, in the sense that the sort function 166can itself call sort(). This did not work reliably in previous releases. 167 168=item #line directives 169 170#line directives now work correctly when they appear at the very 171beginning of C<eval "...">. 172 173=item Subroutine prototypes 174 175The (\&) prototype now works properly. 176 177=item map() 178 179map() could get pathologically slow when the result list it generates 180is larger than the source list. The performance has been improved for 181common scenarios. 182 183=item Debugger 184 185Debugger exit code now reflects the script exit code. 186 187Condition C<"0"> in breakpoints is now treated correctly. 188 189The C<d> command now checks the line number. 190 191C<$.> is no longer corrupted by the debugger. 192 193All debugger output now correctly goes to the socket if RemotePort 194is set. 195 196=item PERL5OPT 197 198PERL5OPT can be set to more than one switch group. Previously, 199it used to be limited to one group of options only. 200 201=item chop() 202 203chop(@list) in list context returned the characters chopped in reverse 204order. This has been reversed to be in the right order. 205 206=item Unicode support 207 208Unicode support has seen a large number of incremental improvements, 209but continues to be highly experimental. It is not expected to be 210fully supported in the 5.6.x maintenance releases. 211 212substr(), join(), repeat(), reverse(), quotemeta() and string 213concatenation were all handling Unicode strings incorrectly in 214Perl 5.6.0. This has been corrected. 215 216Support for C<tr///CU> and C<tr///UC> etc., have been removed since 217we realized the interface is broken. For similar functionality, 218see L<perlfunc/pack>. 219 220The Unicode Character Database has been updated to version 3.0.1 221with additions made available to the public as of August 30, 2000. 222 223The Unicode character classes \p{Blank} and \p{SpacePerl} have been 224added. "Blank" is like C isblank(), that is, it contains only 225"horizontal whitespace" (the space character is, the newline isn't), 226and the "SpacePerl" is the Unicode equivalent of C<\s> (\p{Space} 227isn't, since that includes the vertical tabulator character, whereas 228C<\s> doesn't.) 229 230If you are experimenting with Unicode support in perl, the development 231versions of Perl may have more to offer. In particular, I/O layers 232are now available in the development track, but not in the maintenance 233track, primarily to do backward compatibility issues. Unicode support 234is also evolving rapidly on a daily basis in the development track--the 235maintenance track only reflects the most conservative of these changes. 236 237=item 64-bit support 238 239Support for 64-bit platforms has been improved, but continues to be 240experimental. The level of support varies greatly among platforms. 241 242=item Compiler 243 244The B Compiler and its various backends have had many incremental 245improvements, but they continue to remain highly experimental. Use in 246production environments is discouraged. 247 248The perlcc tool has been rewritten so that the user interface is much 249more like that of a C compiler. 250 251The perlbc tools has been removed. Use C<perlcc -B> instead. 252 253=item Lvalue subroutines 254 255There have been various bugfixes to support lvalue subroutines better. 256However, the feature still remains experimental. 257 258=item IO::Socket 259 260IO::Socket::INET failed to open the specified port if the service 261name was not known. It now correctly uses the supplied port number 262as is. 263 264=item File::Find 265 266File::Find now chdir()s correctly when chasing symbolic links. 267 268=item xsubpp 269 270xsubpp now tolerates embedded POD sections. 271 272=item C<no Module;> 273 274C<no Module;> does not produce an error even if Module does not have an 275unimport() method. This parallels the behavior of C<use> vis-a-vis 276C<import>. 277 278=item Tests 279 280A large number of tests have been added. 281 282=back 283 284=head2 Core features 285 286untie() will now call an UNTIE() hook if it exists. See L<perltie> 287for details. 288 289The C<-DT> command line switch outputs copious tokenizing information. 290See L<perlrun>. 291 292Arrays are now always interpolated in double-quotish strings. Previously, 293C<"foo@bar.com"> used to be a fatal error at compile time, if an array 294C<@bar> was not used or declared. This transitional behavior was 295intended to help migrate perl4 code, and is deemed to be no longer useful. 296See L</"Arrays now always interpolate into double-quoted strings">. 297 298keys(), each(), pop(), push(), shift(), splice() and unshift() 299can all be overridden now. 300 301C<my __PACKAGE__ $obj> now does the expected thing. 302 303=head2 Configuration issues 304 305On some systems (IRIX and Solaris among them) the system malloc is demonstrably 306better. While the defaults haven't been changed in order to retain binary 307compatibility with earlier releases, you may be better off building perl 308with C<Configure -Uusemymalloc ...> as discussed in the F<INSTALL> file. 309 310C<Configure> has been enhanced in various ways: 311 312=over 313 314=item * 315 316Minimizes use of temporary files. 317 318=item * 319 320By default, does not link perl with libraries not used by it, such as 321the various dbm libraries. SunOS 4.x hints preserve behavior on that 322platform. 323 324=item * 325 326Support for pdp11-style memory models has been removed due to obsolescence. 327 328=item * 329 330Building outside the source tree is supported on systems that have 331symbolic links. This is done by running 332 333 sh /path/to/source/Configure -Dmksymlinks ... 334 make all test install 335 336in a directory other than the perl source directory. See F<INSTALL>. 337 338=item * 339 340C<Configure -S> can be run non-interactively. 341 342=back 343 344=head2 Documentation 345 346README.aix, README.solaris and README.macos have been added. 347README.posix-bc has been renamed to README.bs2000. These are 348installed as L<perlaix>, L<perlsolaris>, L<perlmacos>, and 349L<perlbs2000> respectively. 350 351The following pod documents are brand new: 352 353 perlclib Internal replacements for standard C library functions 354 perldebtut Perl debugging tutorial 355 perlebcdic Considerations for running Perl on EBCDIC platforms 356 perlnewmod Perl modules: preparing a new module for distribution 357 perlrequick Perl regular expressions quick start 358 perlretut Perl regular expressions tutorial 359 perlutil utilities packaged with the Perl distribution 360 361The F<INSTALL> file has been expanded to cover various issues, such as 36264-bit support. 363 364A longer list of contributors has been added to the source distribution. 365See the file C<AUTHORS>. 366 367Numerous other changes have been made to the included documentation and FAQs. 368 369=head2 Bundled modules 370 371The following modules have been added. 372 373=over 374 375=item B::Concise 376 377Walks Perl syntax tree, printing concise info about ops. See L<B::Concise>. 378 379=item File::Temp 380 381Returns name and handle of a temporary file safely. See L<File::Temp>. 382 383=item Pod::LaTeX 384 385Converts Pod data to formatted LaTeX. See L<Pod::LaTeX>. 386 387=item Pod::Text::Overstrike 388 389Converts POD data to formatted overstrike text. See L<Pod::Text::Overstrike>. 390 391=back 392 393The following modules have been upgraded. 394 395=over 396 397=item CGI 398 399CGI v2.752 is now included. 400 401=item CPAN 402 403CPAN v1.59_54 is now included. 404 405=item Class::Struct 406 407Various bugfixes have been added. 408 409=item DB_File 410 411DB_File v1.75 supports newer Berkeley DB versions, among other 412improvements. 413 414=item Devel::Peek 415 416Devel::Peek has been enhanced to support dumping of memory statistics, 417when perl is built with the included malloc(). 418 419=item File::Find 420 421File::Find now supports pre and post-processing of the files in order 422to sort() them, etc. 423 424=item Getopt::Long 425 426Getopt::Long v2.25 is included. 427 428=item IO::Poll 429 430Various bug fixes have been included. 431 432=item IPC::Open3 433 434IPC::Open3 allows use of numeric file descriptors. 435 436=item Math::BigFloat 437 438The fmod() function supports modulus operations. Various bug fixes 439have also been included. 440 441=item Math::Complex 442 443Math::Complex handles inf, NaN etc., better. 444 445=item Net::Ping 446 447ping() could fail on odd number of data bytes, and when the echo service 448isn't running. This has been corrected. 449 450=item Opcode 451 452A memory leak has been fixed. 453 454=item Pod::Parser 455 456Version 1.13 of the Pod::Parser suite is included. 457 458=item Pod::Text 459 460Pod::Text and related modules have been upgraded to the versions 461in podlators suite v2.08. 462 463=item SDBM_File 464 465On dosish platforms, some keys went missing because of lack of support for 466files with "holes". A workaround for the problem has been added. 467 468=item Sys::Syslog 469 470Various bug fixes have been included. 471 472=item Tie::RefHash 473 474Now supports Tie::RefHash::Nestable to automagically tie hashref values. 475 476=item Tie::SubstrHash 477 478Various bug fixes have been included. 479 480=back 481 482=head2 Platform-specific improvements 483 484The following new ports are now available. 485 486=over 487 488=item NCR MP-RAS 489 490=item NonStop-UX 491 492=back 493 494Perl now builds under Amdahl UTS. 495 496Perl has also been verified to build under Amiga OS. 497 498Support for EPOC has been much improved. See README.epoc. 499 500Building perl with -Duseithreads or -Duse5005threads now works 501under HP-UX 10.20 (previously it only worked under 10.30 or later). 502You will need a thread library package installed. See README.hpux. 503 504Long doubles should now work under Linux. 505 506Mac OS Classic is now supported in the mainstream source package. 507See README.macos. 508 509Support for MPE/iX has been updated. See README.mpeix. 510 511Support for OS/2 has been improved. See C<os2/Changes> and README.os2. 512 513Dynamic loading on z/OS (formerly OS/390) has been improved. See 514README.os390. 515 516Support for VMS has seen many incremental improvements, including 517better support for operators like backticks and system(), and better 518%ENV handling. See C<README.vms> and L<perlvms>. 519 520Support for Stratus VOS has been improved. See C<vos/Changes> and README.vos. 521 522Support for Windows has been improved. 523 524=over 525 526=item * 527 528fork() emulation has been improved in various ways, but still continues 529to be experimental. See L<perlfork> for known bugs and caveats. 530 531=item * 532 533%SIG has been enabled under USE_ITHREADS, but its use is completely 534unsupported under all configurations. 535 536=item * 537 538Borland C++ v5.5 is now a supported compiler that can build Perl. 539However, the generated binaries continue to be incompatible with those 540generated by the other supported compilers (GCC and Visual C++). 541 542=item * 543 544Non-blocking waits for child processes (or pseudo-processes) are 545supported via C<waitpid($pid, &POSIX::WNOHANG)>. 546 547=item * 548 549A memory leak in accept() has been fixed. 550 551=item * 552 553wait(), waitpid() and backticks now return the correct exit status under 554Windows 9x. 555 556=item * 557 558Trailing new %ENV entries weren't propagated to child processes. This 559is now fixed. 560 561=item * 562 563Current directory entries in %ENV are now correctly propagated to child 564processes. 565 566=item * 567 568Duping socket handles with open(F, ">&MYSOCK") now works under Windows 9x. 569 570=item * 571 572The makefiles now provide a single switch to bulk-enable all the features 573enabled in ActiveState ActivePerl (a popular binary distribution). 574 575=item * 576 577Win32::GetCwd() correctly returns C:\ instead of C: when at the drive root. 578Other bugs in chdir() and Cwd::cwd() have also been fixed. 579 580=item * 581 582fork() correctly returns undef and sets EAGAIN when it runs out of 583pseudo-process handles. 584 585=item * 586 587ExtUtils::MakeMaker now uses $ENV{LIB} to search for libraries. 588 589=item * 590 591UNC path handling is better when perl is built to support fork(). 592 593=item * 594 595A handle leak in socket handling has been fixed. 596 597=item * 598 599send() works from within a pseudo-process. 600 601=back 602 603Unless specifically qualified otherwise, the remainder of this document 604covers changes between the 5.005 and 5.6.0 releases. 605 606=head1 Core Enhancements 607 608=head2 Interpreter cloning, threads, and concurrency 609 610Perl 5.6.0 introduces the beginnings of support for running multiple 611interpreters concurrently in different threads. In conjunction with 612the perl_clone() API call, which can be used to selectively duplicate 613the state of any given interpreter, it is possible to compile a 614piece of code once in an interpreter, clone that interpreter 615one or more times, and run all the resulting interpreters in distinct 616threads. 617 618On the Windows platform, this feature is used to emulate fork() at the 619interpreter level. See L<perlfork> for details about that. 620 621This feature is still in evolution. It is eventually meant to be used 622to selectively clone a subroutine and data reachable from that 623subroutine in a separate interpreter and run the cloned subroutine 624in a separate thread. Since there is no shared data between the 625interpreters, little or no locking will be needed (unless parts of 626the symbol table are explicitly shared). This is obviously intended 627to be an easy-to-use replacement for the existing threads support. 628 629Support for cloning interpreters and interpreter concurrency can be 630enabled using the -Dusethreads Configure option (see win32/Makefile for 631how to enable it on Windows.) The resulting perl executable will be 632functionally identical to one that was built with -Dmultiplicity, but 633the perl_clone() API call will only be available in the former. 634 635-Dusethreads enables the cpp macro USE_ITHREADS by default, which in turn 636enables Perl source code changes that provide a clear separation between 637the op tree and the data it operates with. The former is immutable, and 638can therefore be shared between an interpreter and all of its clones, 639while the latter is considered local to each interpreter, and is therefore 640copied for each clone. 641 642Note that building Perl with the -Dusemultiplicity Configure option 643is adequate if you wish to run multiple B<independent> interpreters 644concurrently in different threads. -Dusethreads only provides the 645additional functionality of the perl_clone() API call and other 646support for running B<cloned> interpreters concurrently. 647 648 NOTE: This is an experimental feature. Implementation details are 649 subject to change. 650 651=head2 Lexically scoped warning categories 652 653You can now control the granularity of warnings emitted by perl at a finer 654level using the C<use warnings> pragma. L<warnings> and L<perllexwarn> 655have copious documentation on this feature. 656 657=head2 Unicode and UTF-8 support 658 659Perl now uses UTF-8 as its internal representation for character 660strings. The C<utf8> and C<bytes> pragmas are used to control this support 661in the current lexical scope. See L<perlunicode>, L<utf8> and L<bytes> for 662more information. 663 664This feature is expected to evolve quickly to support some form of I/O 665disciplines that can be used to specify the kind of input and output data 666(bytes or characters). Until that happens, additional modules from CPAN 667will be needed to complete the toolkit for dealing with Unicode. 668 669 NOTE: This should be considered an experimental feature. Implementation 670 details are subject to change. 671 672=head2 Support for interpolating named characters 673 674The new C<\N> escape interpolates named characters within strings. 675For example, C<"Hi! \N{WHITE SMILING FACE}"> evaluates to a string 676with a Unicode smiley face at the end. 677 678=head2 "our" declarations 679 680An "our" declaration introduces a value that can be best understood 681as a lexically scoped symbolic alias to a global variable in the 682package that was current where the variable was declared. This is 683mostly useful as an alternative to the C<vars> pragma, but also provides 684the opportunity to introduce typing and other attributes for such 685variables. See L<perlfunc/our>. 686 687=head2 Support for strings represented as a vector of ordinals 688 689Literals of the form C<v1.2.3.4> are now parsed as a string composed 690of characters with the specified ordinals. This is an alternative, more 691readable way to construct (possibly Unicode) strings instead of 692interpolating characters, as in C<"\x{1}\x{2}\x{3}\x{4}">. The leading 693C<v> may be omitted if there are more than two ordinals, so C<1.2.3> is 694parsed the same as C<v1.2.3>. 695 696Strings written in this form are also useful to represent version "numbers". 697It is easy to compare such version "numbers" (which are really just plain 698strings) using any of the usual string comparison operators C<eq>, C<ne>, 699C<lt>, C<gt>, etc., or perform bitwise string operations on them using C<|>, 700C<&>, etc. 701 702In conjunction with the new C<$^V> magic variable (which contains 703the perl version as a string), such literals can be used as a readable way 704to check if you're running a particular version of Perl: 705 706 # this will parse in older versions of Perl also 707 if ($^V and $^V gt v5.6.0) { 708 # new features supported 709 } 710 711C<require> and C<use> also have some special magic to support such literals. 712They will be interpreted as a version rather than as a module name: 713 714 require v5.6.0; # croak if $^V lt v5.6.0 715 use v5.6.0; # same, but croaks at compile-time 716 717Alternatively, the C<v> may be omitted if there is more than one dot: 718 719 require 5.6.0; 720 use 5.6.0; 721 722Also, C<sprintf> and C<printf> support the Perl-specific format flag C<%v> 723to print ordinals of characters in arbitrary strings: 724 725 printf "v%vd", $^V; # prints current version, such as "v5.5.650" 726 printf "%*vX", ":", $addr; # formats IPv6 address 727 printf "%*vb", " ", $bits; # displays bitstring 728 729See L<perldata/"Scalar value constructors"> for additional information. 730 731=head2 Improved Perl version numbering system 732 733Beginning with Perl version 5.6.0, the version number convention has been 734changed to a "dotted integer" scheme that is more commonly found in open 735source projects. 736 737Maintenance versions of v5.6.0 will be released as v5.6.1, v5.6.2 etc. 738The next development series following v5.6.0 will be numbered v5.7.x, 739beginning with v5.7.0, and the next major production release following 740v5.6.0 will be v5.8.0. 741 742The English module now sets $PERL_VERSION to $^V (a string value) rather 743than C<$]> (a numeric value). (This is a potential incompatibility. 744Send us a report via perlbug if you are affected by this.) 745 746The v1.2.3 syntax is also now legal in Perl. 747See L<Support for strings represented as a vector of ordinals> for more on that. 748 749To cope with the new versioning system's use of at least three significant 750digits for each version component, the method used for incrementing the 751subversion number has also changed slightly. We assume that versions older 752than v5.6.0 have been incrementing the subversion component in multiples of 75310. Versions after v5.6.0 will increment them by 1. Thus, using the new 754notation, 5.005_03 is the "same" as v5.5.30, and the first maintenance 755version following v5.6.0 will be v5.6.1 (which should be read as being 756equivalent to a floating point value of 5.006_001 in the older format, 757stored in C<$]>). 758 759=head2 New syntax for declaring subroutine attributes 760 761Formerly, if you wanted to mark a subroutine as being a method call or 762as requiring an automatic lock() when it is entered, you had to declare 763that with a C<use attrs> pragma in the body of the subroutine. 764That can now be accomplished with declaration syntax, like this: 765 766 sub mymethod : locked method ; 767 ... 768 sub mymethod : locked method { 769 ... 770 } 771 772 sub othermethod :locked :method ; 773 ... 774 sub othermethod :locked :method { 775 ... 776 } 777 778 779(Note how only the first C<:> is mandatory, and whitespace surrounding 780the C<:> is optional.) 781 782F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes 783with the stubs they provide. See L<attributes>. 784 785=head2 File and directory handles can be autovivified 786 787Similar to how constructs such as C<< $x->[0] >> autovivify a reference, 788handle constructors (open(), opendir(), pipe(), socketpair(), sysopen(), 789socket(), and accept()) now autovivify a file or directory handle 790if the handle passed to them is an uninitialized scalar variable. This 791allows the constructs such as C<open(my $fh, ...)> and C<open(local $fh,...)> 792to be used to create filehandles that will conveniently be closed 793automatically when the scope ends, provided there are no other references 794to them. This largely eliminates the need for typeglobs when opening 795filehandles that must be passed around, as in the following example: 796 797 sub myopen { 798 open my $fh, "@_" 799 or die "Can't open '@_': $!"; 800 return $fh; 801 } 802 803 { 804 my $f = myopen("</etc/motd"); 805 print <$f>; 806 # $f implicitly closed here 807 } 808 809=head2 open() with more than two arguments 810 811If open() is passed three arguments instead of two, the second argument 812is used as the mode and the third argument is taken to be the file name. 813This is primarily useful for protecting against unintended magic behavior 814of the traditional two-argument form. See L<perlfunc/open>. 815 816=head2 64-bit support 817 818Any platform that has 64-bit integers either 819 820 (1) natively as longs or ints 821 (2) via special compiler flags 822 (3) using long long or int64_t 823 824is able to use "quads" (64-bit integers) as follows: 825 826=over 4 827 828=item * 829 830constants (decimal, hexadecimal, octal, binary) in the code 831 832=item * 833 834arguments to oct() and hex() 835 836=item * 837 838arguments to print(), printf() and sprintf() (flag prefixes ll, L, q) 839 840=item * 841 842printed as such 843 844=item * 845 846pack() and unpack() "q" and "Q" formats 847 848=item * 849 850in basic arithmetics: + - * / % (NOTE: operating close to the limits 851of the integer values may produce surprising results) 852 853=item * 854 855in bit arithmetics: & | ^ ~ << >> (NOTE: these used to be forced 856to be 32 bits wide but now operate on the full native width.) 857 858=item * 859 860vec() 861 862=back 863 864Note that unless you have the case (a) you will have to configure 865and compile Perl using the -Duse64bitint Configure flag. 866 867 NOTE: The Configure flags -Duselonglong and -Duse64bits have been 868 deprecated. Use -Duse64bitint instead. 869 870There are actually two modes of 64-bitness: the first one is achieved 871using Configure -Duse64bitint and the second one using Configure 872-Duse64bitall. The difference is that the first one is minimal and 873the second one maximal. The first works in more places than the second. 874 875The C<use64bitint> does only as much as is required to get 64-bit 876integers into Perl (this may mean, for example, using "long longs") 877while your memory may still be limited to 2 gigabytes (because your 878pointers could still be 32-bit). Note that the name C<64bitint> does 879not imply that your C compiler will be using 64-bit C<int>s (it might, 880but it doesn't have to): the C<use64bitint> means that you will be 881able to have 64 bits wide scalar values. 882 883The C<use64bitall> goes all the way by attempting to switch also 884integers (if it can), longs (and pointers) to being 64-bit. This may 885create an even more binary incompatible Perl than -Duse64bitint: the 886resulting executable may not run at all in a 32-bit box, or you may 887have to reboot/reconfigure/rebuild your operating system to be 64-bit 888aware. 889 890Natively 64-bit systems like Alpha and Cray need neither -Duse64bitint 891nor -Duse64bitall. 892 893Last but not least: note that due to Perl's habit of always using 894floating point numbers, the quads are still not true integers. 895When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned, 896-9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they 897are silently promoted to floating point numbers, after which they will 898start losing precision (in their lower digits). 899 900 NOTE: 64-bit support is still experimental on most platforms. 901 Existing support only covers the LP64 data model. In particular, the 902 LLP64 data model is not yet supported. 64-bit libraries and system 903 APIs on many platforms have not stabilized--your mileage may vary. 904 905=head2 Large file support 906 907If you have filesystems that support "large files" (files larger than 9082 gigabytes), you may now also be able to create and access them from 909Perl. 910 911 NOTE: The default action is to enable large file support, if 912 available on the platform. 913 914If the large file support is on, and you have a Fcntl constant 915O_LARGEFILE, the O_LARGEFILE is automatically added to the flags 916of sysopen(). 917 918Beware that unless your filesystem also supports "sparse files" seeking 919to umpteen petabytes may be inadvisable. 920 921Note that in addition to requiring a proper file system to do large 922files you may also need to adjust your per-process (or your 923per-system, or per-process-group, or per-user-group) maximum filesize 924limits before running Perl scripts that try to handle large files, 925especially if you intend to write such files. 926 927Finally, in addition to your process/process group maximum filesize 928limits, you may have quota limits on your filesystems that stop you 929(your user id or your user group id) from using large files. 930 931Adjusting your process/user/group/file system/operating system limits 932is outside the scope of Perl core language. For process limits, you 933may try increasing the limits using your shell's limits/limit/ulimit 934command before running Perl. The BSD::Resource extension (not 935included with the standard Perl distribution) may also be of use, it 936offers the getrlimit/setrlimit interface that can be used to adjust 937process resource usage limits, including the maximum filesize limit. 938 939=head2 Long doubles 940 941In some systems you may be able to use long doubles to enhance the 942range and precision of your double precision floating point numbers 943(that is, Perl's numbers). Use Configure -Duselongdouble to enable 944this support (if it is available). 945 946=head2 "more bits" 947 948You can "Configure -Dusemorebits" to turn on both the 64-bit support 949and the long double support. 950 951=head2 Enhanced support for sort() subroutines 952 953Perl subroutines with a prototype of C<($$)>, and XSUBs in general, can 954now be used as sort subroutines. In either case, the two elements to 955be compared are passed as normal parameters in @_. See L<perlfunc/sort>. 956 957For unprototyped sort subroutines, the historical behavior of passing 958the elements to be compared as the global variables $a and $b remains 959unchanged. 960 961=head2 C<sort $coderef @foo> allowed 962 963sort() did not accept a subroutine reference as the comparison 964function in earlier versions. This is now permitted. 965 966=head2 File globbing implemented internally 967 968Perl now uses the File::Glob implementation of the glob() operator 969automatically. This avoids using an external csh process and the 970problems associated with it. 971 972 NOTE: This is currently an experimental feature. Interfaces and 973 implementation are subject to change. 974 975=head2 Support for CHECK blocks 976 977In addition to C<BEGIN>, C<INIT>, C<END>, C<DESTROY> and C<AUTOLOAD>, 978subroutines named C<CHECK> are now special. These are queued up during 979compilation and behave similar to END blocks, except they are called at 980the end of compilation rather than at the end of execution. They cannot 981be called directly. 982 983=head2 POSIX character class syntax [: :] supported 984 985For example to match alphabetic characters use /[[:alpha:]]/. 986See L<perlre> for details. 987 988=head2 Better pseudo-random number generator 989 990In 5.005_0x and earlier, perl's rand() function used the C library 991rand(3) function. As of 5.005_52, Configure tests for drand48(), 992random(), and rand() (in that order) and picks the first one it finds. 993 994These changes should result in better random numbers from rand(). 995 996=head2 Improved C<qw//> operator 997 998The C<qw//> operator is now evaluated at compile time into a true list 999instead of being replaced with a run time call to C<split()>. This 1000removes the confusing misbehaviour of C<qw//> in scalar context, which 1001had inherited that behaviour from split(). 1002 1003Thus: 1004 1005 $foo = ($bar) = qw(a b c); print "$foo|$bar\n"; 1006 1007now correctly prints "3|a", instead of "2|a". 1008 1009=head2 Better worst-case behavior of hashes 1010 1011Small changes in the hashing algorithm have been implemented in 1012order to improve the distribution of lower order bits in the 1013hashed value. This is expected to yield better performance on 1014keys that are repeated sequences. 1015 1016=head2 pack() format 'Z' supported 1017 1018The new format type 'Z' is useful for packing and unpacking null-terminated 1019strings. See L<perlfunc/"pack">. 1020 1021=head2 pack() format modifier '!' supported 1022 1023The new format type modifier '!' is useful for packing and unpacking 1024native shorts, ints, and longs. See L<perlfunc/"pack">. 1025 1026=head2 pack() and unpack() support counted strings 1027 1028The template character '/' can be used to specify a counted string 1029type to be packed or unpacked. See L<perlfunc/"pack">. 1030 1031=head2 Comments in pack() templates 1032 1033The '#' character in a template introduces a comment up to 1034end of the line. This facilitates documentation of pack() 1035templates. 1036 1037=head2 Weak references 1038 1039In previous versions of Perl, you couldn't cache objects so as 1040to allow them to be deleted if the last reference from outside 1041the cache is deleted. The reference in the cache would hold a 1042reference count on the object and the objects would never be 1043destroyed. 1044 1045Another familiar problem is with circular references. When an 1046object references itself, its reference count would never go 1047down to zero, and it would not get destroyed until the program 1048is about to exit. 1049 1050Weak references solve this by allowing you to "weaken" any 1051reference, that is, make it not count towards the reference count. 1052When the last non-weak reference to an object is deleted, the object 1053is destroyed and all the weak references to the object are 1054automatically undef-ed. 1055 1056To use this feature, you need the Devel::WeakRef package from CPAN, which 1057contains additional documentation. 1058 1059 NOTE: This is an experimental feature. Details are subject to change. 1060 1061=head2 Binary numbers supported 1062 1063Binary numbers are now supported as literals, in s?printf formats, and 1064C<oct()>: 1065 1066 $answer = 0b101010; 1067 printf "The answer is: %b\n", oct("0b101010"); 1068 1069=head2 Lvalue subroutines 1070 1071Subroutines can now return modifiable lvalues. 1072See L<perlsub/"Lvalue subroutines">. 1073 1074 NOTE: This is an experimental feature. Details are subject to change. 1075 1076=head2 Some arrows may be omitted in calls through references 1077 1078Perl now allows the arrow to be omitted in many constructs 1079involving subroutine calls through references. For example, 1080C<< $foo[10]->('foo') >> may now be written C<$foo[10]('foo')>. 1081This is rather similar to how the arrow may be omitted from 1082C<< $foo[10]->{'foo'} >>. Note however, that the arrow is still 1083required for C<< foo(10)->('bar') >>. 1084 1085=head2 Boolean assignment operators are legal lvalues 1086 1087Constructs such as C<($a ||= 2) += 1> are now allowed. 1088 1089=head2 exists() is supported on subroutine names 1090 1091The exists() builtin now works on subroutine names. A subroutine 1092is considered to exist if it has been declared (even if implicitly). 1093See L<perlfunc/exists> for examples. 1094 1095=head2 exists() and delete() are supported on array elements 1096 1097The exists() and delete() builtins now work on simple arrays as well. 1098The behavior is similar to that on hash elements. 1099 1100exists() can be used to check whether an array element has been 1101initialized. This avoids autovivifying array elements that don't exist. 1102If the array is tied, the EXISTS() method in the corresponding tied 1103package will be invoked. 1104 1105delete() may be used to remove an element from the array and return 1106it. The array element at that position returns to its uninitialized 1107state, so that testing for the same element with exists() will return 1108false. If the element happens to be the one at the end, the size of 1109the array also shrinks up to the highest element that tests true for 1110exists(), or 0 if none such is found. If the array is tied, the DELETE() 1111method in the corresponding tied package will be invoked. 1112 1113See L<perlfunc/exists> and L<perlfunc/delete> for examples. 1114 1115=head2 Pseudo-hashes work better 1116 1117Dereferencing some types of reference values in a pseudo-hash, 1118such as C<< $ph->{foo}[1] >>, was accidentally disallowed. This has 1119been corrected. 1120 1121When applied to a pseudo-hash element, exists() now reports whether 1122the specified value exists, not merely if the key is valid. 1123 1124delete() now works on pseudo-hashes. When given a pseudo-hash element 1125or slice it deletes the values corresponding to the keys (but not the keys 1126themselves). See L<perlref/"Pseudo-hashes: Using an array as a hash">. 1127 1128Pseudo-hash slices with constant keys are now optimized to array lookups 1129at compile-time. 1130 1131List assignments to pseudo-hash slices are now supported. 1132 1133The C<fields> pragma now provides ways to create pseudo-hashes, via 1134fields::new() and fields::phash(). See L<fields>. 1135 1136 NOTE: The pseudo-hash data type continues to be experimental. 1137 Limiting oneself to the interface elements provided by the 1138 fields pragma will provide protection from any future changes. 1139 1140=head2 Automatic flushing of output buffers 1141 1142fork(), exec(), system(), qx//, and pipe open()s now flush buffers 1143of all files opened for output when the operation was attempted. This 1144mostly eliminates confusing buffering mishaps suffered by users unaware 1145of how Perl internally handles I/O. 1146 1147This is not supported on some platforms like Solaris where a suitably 1148correct implementation of fflush(NULL) isn't available. 1149 1150=head2 Better diagnostics on meaningless filehandle operations 1151 1152Constructs such as C<< open(<FH>) >> and C<< close(<FH>) >> 1153are compile time errors. Attempting to read from filehandles that 1154were opened only for writing will now produce warnings (just as 1155writing to read-only filehandles does). 1156 1157=head2 Where possible, buffered data discarded from duped input filehandle 1158 1159C<< open(NEW, "<&OLD") >> now attempts to discard any data that 1160was previously read and buffered in C<OLD> before duping the handle. 1161On platforms where doing this is allowed, the next read operation 1162on C<NEW> will return the same data as the corresponding operation 1163on C<OLD>. Formerly, it would have returned the data from the start 1164of the following disk block instead. 1165 1166=head2 eof() has the same old magic as <> 1167 1168C<eof()> would return true if no attempt to read from C<< <> >> had 1169yet been made. C<eof()> has been changed to have a little magic of its 1170own, it now opens the C<< <> >> files. 1171 1172=head2 binmode() can be used to set :crlf and :raw modes 1173 1174binmode() now accepts a second argument that specifies a discipline 1175for the handle in question. The two pseudo-disciplines ":raw" and 1176":crlf" are currently supported on DOS-derivative platforms. 1177See L<perlfunc/"binmode"> and L<open>. 1178 1179=head2 C<-T> filetest recognizes UTF-8 encoded files as "text" 1180 1181The algorithm used for the C<-T> filetest has been enhanced to 1182correctly identify UTF-8 content as "text". 1183 1184=head2 system(), backticks and pipe open now reflect exec() failure 1185 1186On Unix and similar platforms, system(), qx() and open(FOO, "cmd |") 1187etc., are implemented via fork() and exec(). When the underlying 1188exec() fails, earlier versions did not report the error properly, 1189since the exec() happened to be in a different process. 1190 1191The child process now communicates with the parent about the 1192error in launching the external command, which allows these 1193constructs to return with their usual error value and set $!. 1194 1195=head2 Improved diagnostics 1196 1197Line numbers are no longer suppressed (under most likely circumstances) 1198during the global destruction phase. 1199 1200Diagnostics emitted from code running in threads other than the main 1201thread are now accompanied by the thread ID. 1202 1203Embedded null characters in diagnostics now actually show up. They 1204used to truncate the message in prior versions. 1205 1206$foo::a and $foo::b are now exempt from "possible typo" warnings only 1207if sort() is encountered in package C<foo>. 1208 1209Unrecognized alphabetic escapes encountered when parsing quote 1210constructs now generate a warning, since they may take on new 1211semantics in later versions of Perl. 1212 1213Many diagnostics now report the internal operation in which the warning 1214was provoked, like so: 1215 1216 Use of uninitialized value in concatenation (.) at (eval 1) line 1. 1217 Use of uninitialized value in print at (eval 1) line 1. 1218 1219Diagnostics that occur within eval may also report the file and line 1220number where the eval is located, in addition to the eval sequence 1221number and the line number within the evaluated text itself. For 1222example: 1223 1224 Not enough arguments for scalar at (eval 4)[newlib/perl5db.pl:1411] line 2, at EOF 1225 1226=head2 Diagnostics follow STDERR 1227 1228Diagnostic output now goes to whichever file the C<STDERR> handle 1229is pointing at, instead of always going to the underlying C runtime 1230library's C<stderr>. 1231 1232=head2 More consistent close-on-exec behavior 1233 1234On systems that support a close-on-exec flag on filehandles, the 1235flag is now set for any handles created by pipe(), socketpair(), 1236socket(), and accept(), if that is warranted by the value of $^F 1237that may be in effect. Earlier versions neglected to set the flag 1238for handles created with these operators. See L<perlfunc/pipe>, 1239L<perlfunc/socketpair>, L<perlfunc/socket>, L<perlfunc/accept>, 1240and L<perlvar/$^F>. 1241 1242=head2 syswrite() ease-of-use 1243 1244The length argument of C<syswrite()> has become optional. 1245 1246=head2 Better syntax checks on parenthesized unary operators 1247 1248Expressions such as: 1249 1250 print defined(&foo,&bar,&baz); 1251 print uc("foo","bar","baz"); 1252 undef($foo,&bar); 1253 1254used to be accidentally allowed in earlier versions, and produced 1255unpredictable behaviour. Some produced ancillary warnings 1256when used in this way; others silently did the wrong thing. 1257 1258The parenthesized forms of most unary operators that expect a single 1259argument now ensure that they are not called with more than one 1260argument, making the cases shown above syntax errors. The usual 1261behaviour of: 1262 1263 print defined &foo, &bar, &baz; 1264 print uc "foo", "bar", "baz"; 1265 undef $foo, &bar; 1266 1267remains unchanged. See L<perlop>. 1268 1269=head2 Bit operators support full native integer width 1270 1271The bit operators (& | ^ ~ << >>) now operate on the full native 1272integral width (the exact size of which is available in $Config{ivsize}). 1273For example, if your platform is either natively 64-bit or if Perl 1274has been configured to use 64-bit integers, these operations apply 1275to 8 bytes (as opposed to 4 bytes on 32-bit platforms). 1276For portability, be sure to mask off the excess bits in the result of 1277unary C<~>, e.g., C<~$x & 0xffffffff>. 1278 1279=head2 Improved security features 1280 1281More potentially unsafe operations taint their results for improved 1282security. 1283 1284The C<passwd> and C<shell> fields returned by the getpwent(), getpwnam(), 1285and getpwuid() are now tainted, because the user can affect their own 1286encrypted password and login shell. 1287 1288The variable modified by shmread(), and messages returned by msgrcv() 1289(and its object-oriented interface IPC::SysV::Msg::rcv) are also tainted, 1290because other untrusted processes can modify messages and shared memory 1291segments for their own nefarious purposes. 1292 1293=head2 More functional bareword prototype (*) 1294 1295Bareword prototypes have been rationalized to enable them to be used 1296to override builtins that accept barewords and interpret them in 1297a special way, such as C<require> or C<do>. 1298 1299Arguments prototyped as C<*> will now be visible within the subroutine 1300as either a simple scalar or as a reference to a typeglob. 1301See L<perlsub/Prototypes>. 1302 1303=head2 C<require> and C<do> may be overridden 1304 1305C<require> and C<do 'file'> operations may be overridden locally 1306by importing subroutines of the same name into the current package 1307(or globally by importing them into the CORE::GLOBAL:: namespace). 1308Overriding C<require> will also affect C<use>, provided the override 1309is visible at compile-time. 1310See L<perlsub/"Overriding Built-in Functions">. 1311 1312=head2 $^X variables may now have names longer than one character 1313 1314Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax 1315error. Now variable names that begin with a control character may be 1316arbitrarily long. However, for compatibility reasons, these variables 1317I<must> be written with explicit braces, as C<${^XY}> for example. 1318C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more 1319than one control character, such as C<${^XY^Z}>, are illegal. 1320 1321The old syntax has not changed. As before, `^X' may be either a 1322literal control-X character or the two-character sequence `caret' plus 1323`X'. When braces are omitted, the variable name stops after the 1324control character. Thus C<"$^XYZ"> continues to be synonymous with 1325C<$^X . "YZ"> as before. 1326 1327As before, lexical variables may not have names beginning with control 1328characters. As before, variables whose names begin with a control 1329character are always forced to be in package `main'. All such variables 1330are reserved for future extensions, except those that begin with 1331C<^_>, which may be used by user programs and are guaranteed not to 1332acquire special meaning in any future version of Perl. 1333 1334=head2 New variable $^C reflects C<-c> switch 1335 1336C<$^C> has a boolean value that reflects whether perl is being run 1337in compile-only mode (i.e. via the C<-c> switch). Since 1338BEGIN blocks are executed under such conditions, this variable 1339enables perl code to determine whether actions that make sense 1340only during normal running are warranted. See L<perlvar>. 1341 1342=head2 New variable $^V contains Perl version as a string 1343 1344C<$^V> contains the Perl version number as a string composed of 1345characters whose ordinals match the version numbers, i.e. v5.6.0. 1346This may be used in string comparisons. 1347 1348See C<Support for strings represented as a vector of ordinals> for an 1349example. 1350 1351=head2 Optional Y2K warnings 1352 1353If Perl is built with the cpp macro C<PERL_Y2KWARN> defined, 1354it emits optional warnings when concatenating the number 19 1355with another number. 1356 1357This behavior must be specifically enabled when running Configure. 1358See F<INSTALL> and F<README.Y2K>. 1359 1360=head2 Arrays now always interpolate into double-quoted strings 1361 1362In double-quoted strings, arrays now interpolate, no matter what. The 1363behavior in earlier versions of perl 5 was that arrays would interpolate 1364into strings if the array had been mentioned before the string was 1365compiled, and otherwise Perl would raise a fatal compile-time error. 1366In versions 5.000 through 5.003, the error was 1367 1368 Literal @example now requires backslash 1369 1370In versions 5.004_01 through 5.6.0, the error was 1371 1372 In string, @example now must be written as \@example 1373 1374The idea here was to get people into the habit of writing 1375C<"fred\@example.com"> when they wanted a literal C<@> sign, just as 1376they have always written C<"Give me back my \$5"> when they wanted a 1377literal C<$> sign. 1378 1379Starting with 5.6.1, when Perl now sees an C<@> sign in a 1380double-quoted string, it I<always> attempts to interpolate an array, 1381regardless of whether or not the array has been used or declared 1382already. The fatal error has been downgraded to an optional warning: 1383 1384 Possible unintended interpolation of @example in string 1385 1386This warns you that C<"fred@example.com"> is going to turn into 1387C<fred.com> if you don't backslash the C<@>. 1388See http://www.plover.com/~mjd/perl/at-error.html for more details 1389about the history here. 1390 1391=head1 Modules and Pragmata 1392 1393=head2 Modules 1394 1395=over 4 1396 1397=item attributes 1398 1399While used internally by Perl as a pragma, this module also 1400provides a way to fetch subroutine and variable attributes. 1401See L<attributes>. 1402 1403=item B 1404 1405The Perl Compiler suite has been extensively reworked for this 1406release. More of the standard Perl testsuite passes when run 1407under the Compiler, but there is still a significant way to 1408go to achieve production quality compiled executables. 1409 1410 NOTE: The Compiler suite remains highly experimental. The 1411 generated code may not be correct, even when it manages to execute 1412 without errors. 1413 1414=item Benchmark 1415 1416Overall, Benchmark results exhibit lower average error and better timing 1417accuracy. 1418 1419You can now run tests for I<n> seconds instead of guessing the right 1420number of tests to run: e.g., timethese(-5, ...) will run each 1421code for at least 5 CPU seconds. Zero as the "number of repetitions" 1422means "for at least 3 CPU seconds". The output format has also 1423changed. For example: 1424 1425 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}}) 1426 1427will now output something like this: 1428 1429 Benchmark: running a, b, each for at least 5 CPU seconds... 1430 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516) 1431 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686) 1432 1433New features: "each for at least N CPU seconds...", "wallclock secs", 1434and the "@ operations/CPU second (n=operations)". 1435 1436timethese() now returns a reference to a hash of Benchmark objects containing 1437the test results, keyed on the names of the tests. 1438 1439timethis() now returns the iterations field in the Benchmark result object 1440instead of 0. 1441 1442timethese(), timethis(), and the new cmpthese() (see below) can also take 1443a format specifier of 'none' to suppress output. 1444 1445A new function countit() is just like timeit() except that it takes a 1446TIME instead of a COUNT. 1447 1448A new function cmpthese() prints a chart comparing the results of each test 1449returned from a timethese() call. For each possible pair of tests, the 1450percentage speed difference (iters/sec or seconds/iter) is shown. 1451 1452For other details, see L<Benchmark>. 1453 1454=item ByteLoader 1455 1456The ByteLoader is a dedicated extension to generate and run 1457Perl bytecode. See L<ByteLoader>. 1458 1459=item constant 1460 1461References can now be used. 1462 1463The new version also allows a leading underscore in constant names, but 1464disallows a double leading underscore (as in "__LINE__"). Some other names 1465are disallowed or warned against, including BEGIN, END, etc. Some names 1466which were forced into main:: used to fail silently in some cases; now they're 1467fatal (outside of main::) and an optional warning (inside of main::). 1468The ability to detect whether a constant had been set with a given name has 1469been added. 1470 1471See L<constant>. 1472 1473=item charnames 1474 1475This pragma implements the C<\N> string escape. See L<charnames>. 1476 1477=item Data::Dumper 1478 1479A C<Maxdepth> setting can be specified to avoid venturing 1480too deeply into deep data structures. See L<Data::Dumper>. 1481 1482The XSUB implementation of Dump() is now automatically called if the 1483C<Useqq> setting is not in use. 1484 1485Dumping C<qr//> objects works correctly. 1486 1487=item DB 1488 1489C<DB> is an experimental module that exposes a clean abstraction 1490to Perl's debugging API. 1491 1492=item DB_File 1493 1494DB_File can now be built with Berkeley DB versions 1, 2 or 3. 1495See C<ext/DB_File/Changes>. 1496 1497=item Devel::DProf 1498 1499Devel::DProf, a Perl source code profiler has been added. See 1500L<Devel::DProf> and L<dprofpp>. 1501 1502=item Devel::Peek 1503 1504The Devel::Peek module provides access to the internal representation 1505of Perl variables and data. It is a data debugging tool for the XS programmer. 1506 1507=item Dumpvalue 1508 1509The Dumpvalue module provides screen dumps of Perl data. 1510 1511=item DynaLoader 1512 1513DynaLoader now supports a dl_unload_file() function on platforms that 1514support unloading shared objects using dlclose(). 1515 1516Perl can also optionally arrange to unload all extension shared objects 1517loaded by Perl. To enable this, build Perl with the Configure option 1518C<-Accflags=-DDL_UNLOAD_ALL_AT_EXIT>. (This maybe useful if you are 1519using Apache with mod_perl.) 1520 1521=item English 1522 1523$PERL_VERSION now stands for C<$^V> (a string value) rather than for C<$]> 1524(a numeric value). 1525 1526=item Env 1527 1528Env now supports accessing environment variables like PATH as array 1529variables. 1530 1531=item Fcntl 1532 1533More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for 1534large file (more than 4GB) access (NOTE: the O_LARGEFILE is 1535automatically added to sysopen() flags if large file support has been 1536configured, as is the default), Free/Net/OpenBSD locking behaviour 1537flags F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined 1538mask of O_RDONLY, O_WRONLY, and O_RDWR. The seek()/sysseek() 1539constants SEEK_SET, SEEK_CUR, and SEEK_END are available via the 1540C<:seek> tag. The chmod()/stat() S_IF* constants and S_IS* functions 1541are available via the C<:mode> tag. 1542 1543=item File::Compare 1544 1545A compare_text() function has been added, which allows custom 1546comparison functions. See L<File::Compare>. 1547 1548=item File::Find 1549 1550File::Find now works correctly when the wanted() function is either 1551autoloaded or is a symbolic reference. 1552 1553A bug that caused File::Find to lose track of the working directory 1554when pruning top-level directories has been fixed. 1555 1556File::Find now also supports several other options to control its 1557behavior. It can follow symbolic links if the C<follow> option is 1558specified. Enabling the C<no_chdir> option will make File::Find skip 1559changing the current directory when walking directories. The C<untaint> 1560flag can be useful when running with taint checks enabled. 1561 1562See L<File::Find>. 1563 1564=item File::Glob 1565 1566This extension implements BSD-style file globbing. By default, 1567it will also be used for the internal implementation of the glob() 1568operator. See L<File::Glob>. 1569 1570=item File::Spec 1571 1572New methods have been added to the File::Spec module: devnull() returns 1573the name of the null device (/dev/null on Unix) and tmpdir() the name of 1574the temp directory (normally /tmp on Unix). There are now also methods 1575to convert between absolute and relative filenames: abs2rel() and 1576rel2abs(). For compatibility with operating systems that specify volume 1577names in file paths, the splitpath(), splitdir(), and catdir() methods 1578have been added. 1579 1580=item File::Spec::Functions 1581 1582The new File::Spec::Functions modules provides a function interface 1583to the File::Spec module. Allows shorthand 1584 1585 $fullname = catfile($dir1, $dir2, $file); 1586 1587instead of 1588 1589 $fullname = File::Spec->catfile($dir1, $dir2, $file); 1590 1591=item Getopt::Long 1592 1593Getopt::Long licensing has changed to allow the Perl Artistic License 1594as well as the GPL. It used to be GPL only, which got in the way of 1595non-GPL applications that wanted to use Getopt::Long. 1596 1597Getopt::Long encourages the use of Pod::Usage to produce help 1598messages. For example: 1599 1600 use Getopt::Long; 1601 use Pod::Usage; 1602 my $man = 0; 1603 my $help = 0; 1604 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2); 1605 pod2usage(1) if $help; 1606 pod2usage(-exitstatus => 0, -verbose => 2) if $man; 1607 1608 __END__ 1609 1610 =head1 NAME 1611 1612 sample - Using Getopt::Long and Pod::Usage 1613 1614 =head1 SYNOPSIS 1615 1616 sample [options] [file ...] 1617 1618 Options: 1619 -help brief help message 1620 -man full documentation 1621 1622 =head1 OPTIONS 1623 1624 =over 8 1625 1626 =item B<-help> 1627 1628 Print a brief help message and exits. 1629 1630 =item B<-man> 1631 1632 Prints the manual page and exits. 1633 1634 =back 1635 1636 =head1 DESCRIPTION 1637 1638 B<This program> will read the given input file(s) and do something 1639 useful with the contents thereof. 1640 1641 =cut 1642 1643See L<Pod::Usage> for details. 1644 1645A bug that prevented the non-option call-back <> from being 1646specified as the first argument has been fixed. 1647 1648To specify the characters < and > as option starters, use ><. Note, 1649however, that changing option starters is strongly deprecated. 1650 1651=item IO 1652 1653write() and syswrite() will now accept a single-argument 1654form of the call, for consistency with Perl's syswrite(). 1655 1656You can now create a TCP-based IO::Socket::INET without forcing 1657a connect attempt. This allows you to configure its options 1658(like making it non-blocking) and then call connect() manually. 1659 1660A bug that prevented the IO::Socket::protocol() accessor 1661from ever returning the correct value has been corrected. 1662 1663IO::Socket::connect now uses non-blocking IO instead of alarm() 1664to do connect timeouts. 1665 1666IO::Socket::accept now uses select() instead of alarm() for doing 1667timeouts. 1668 1669IO::Socket::INET->new now sets $! correctly on failure. $@ is 1670still set for backwards compatibility. 1671 1672=item JPL 1673 1674Java Perl Lingo is now distributed with Perl. See jpl/README 1675for more information. 1676 1677=item lib 1678 1679C<use lib> now weeds out any trailing duplicate entries. 1680C<no lib> removes all named entries. 1681 1682=item Math::BigInt 1683 1684The bitwise operations C<<< << >>>, C<<< >> >>>, C<&>, C<|>, 1685and C<~> are now supported on bigints. 1686 1687=item Math::Complex 1688 1689The accessor methods Re, Im, arg, abs, rho, and theta can now also 1690act as mutators (accessor $z->Re(), mutator $z->Re(3)). 1691 1692The class method C<display_format> and the corresponding object method 1693C<display_format>, in addition to accepting just one argument, now can 1694also accept a parameter hash. Recognized keys of a parameter hash are 1695C<"style">, which corresponds to the old one parameter case, and two 1696new parameters: C<"format">, which is a printf()-style format string 1697(defaults usually to C<"%.15g">, you can revert to the default by 1698setting the format string to C<undef>) used for both parts of a 1699complex number, and C<"polar_pretty_print"> (defaults to true), 1700which controls whether an attempt is made to try to recognize small 1701multiples and rationals of pi (2pi, pi/2) at the argument (angle) of a 1702polar complex number. 1703 1704The potentially disruptive change is that in list context both methods 1705now I<return the parameter hash>, instead of only the value of the 1706C<"style"> parameter. 1707 1708=item Math::Trig 1709 1710A little bit of radial trigonometry (cylindrical and spherical), 1711radial coordinate conversions, and the great circle distance were added. 1712 1713=item Pod::Parser, Pod::InputObjects 1714 1715Pod::Parser is a base class for parsing and selecting sections of 1716pod documentation from an input stream. This module takes care of 1717identifying pod paragraphs and commands in the input and hands off the 1718parsed paragraphs and commands to user-defined methods which are free 1719to interpret or translate them as they see fit. 1720 1721Pod::InputObjects defines some input objects needed by Pod::Parser, and 1722for advanced users of Pod::Parser that need more about a command besides 1723its name and text. 1724 1725As of release 5.6.0 of Perl, Pod::Parser is now the officially sanctioned 1726"base parser code" recommended for use by all pod2xxx translators. 1727Pod::Text (pod2text) and Pod::Man (pod2man) have already been converted 1728to use Pod::Parser and efforts to convert Pod::HTML (pod2html) are already 1729underway. For any questions or comments about pod parsing and translating 1730issues and utilities, please use the pod-people@perl.org mailing list. 1731 1732For further information, please see L<Pod::Parser> and L<Pod::InputObjects>. 1733 1734=item Pod::Checker, podchecker 1735 1736This utility checks pod files for correct syntax, according to 1737L<perlpod>. Obvious errors are flagged as such, while warnings are 1738printed for mistakes that can be handled gracefully. The checklist is 1739not complete yet. See L<Pod::Checker>. 1740 1741=item Pod::ParseUtils, Pod::Find 1742 1743These modules provide a set of gizmos that are useful mainly for pod 1744translators. L<Pod::Find|Pod::Find> traverses directory structures and 1745returns found pod files, along with their canonical names (like 1746C<File::Spec::Unix>). L<Pod::ParseUtils|Pod::ParseUtils> contains 1747B<Pod::List> (useful for storing pod list information), B<Pod::Hyperlink> 1748(for parsing the contents of C<LE<lt>E<gt>> sequences) and B<Pod::Cache> 1749(for caching information about pod files, e.g., link nodes). 1750 1751=item Pod::Select, podselect 1752 1753Pod::Select is a subclass of Pod::Parser which provides a function 1754named "podselect()" to filter out user-specified sections of raw pod 1755documentation from an input stream. podselect is a script that provides 1756access to Pod::Select from other scripts to be used as a filter. 1757See L<Pod::Select>. 1758 1759=item Pod::Usage, pod2usage 1760 1761Pod::Usage provides the function "pod2usage()" to print usage messages for 1762a Perl script based on its embedded pod documentation. The pod2usage() 1763function is generally useful to all script authors since it lets them 1764write and maintain a single source (the pods) for documentation, thus 1765removing the need to create and maintain redundant usage message text 1766consisting of information already in the pods. 1767 1768There is also a pod2usage script which can be used from other kinds of 1769scripts to print usage messages from pods (even for non-Perl scripts 1770with pods embedded in comments). 1771 1772For details and examples, please see L<Pod::Usage>. 1773 1774=item Pod::Text and Pod::Man 1775 1776Pod::Text has been rewritten to use Pod::Parser. While pod2text() is 1777still available for backwards compatibility, the module now has a new 1778preferred interface. See L<Pod::Text> for the details. The new Pod::Text 1779module is easily subclassed for tweaks to the output, and two such 1780subclasses (Pod::Text::Termcap for man-page-style bold and underlining 1781using termcap information, and Pod::Text::Color for markup with ANSI color 1782sequences) are now standard. 1783 1784pod2man has been turned into a module, Pod::Man, which also uses 1785Pod::Parser. In the process, several outstanding bugs related to quotes 1786in section headers, quoting of code escapes, and nested lists have been 1787fixed. pod2man is now a wrapper script around this module. 1788 1789=item SDBM_File 1790 1791An EXISTS method has been added to this module (and sdbm_exists() has 1792been added to the underlying sdbm library), so one can now call exists 1793on an SDBM_File tied hash and get the correct result, rather than a 1794runtime error. 1795 1796A bug that may have caused data loss when more than one disk block 1797happens to be read from the database in a single FETCH() has been 1798fixed. 1799 1800=item Sys::Syslog 1801 1802Sys::Syslog now uses XSUBs to access facilities from syslog.h so it 1803no longer requires syslog.ph to exist. 1804 1805=item Sys::Hostname 1806 1807Sys::Hostname now uses XSUBs to call the C library's gethostname() or 1808uname() if they exist. 1809 1810=item Term::ANSIColor 1811 1812Term::ANSIColor is a very simple module to provide easy and readable 1813access to the ANSI color and highlighting escape sequences, supported by 1814most ANSI terminal emulators. It is now included standard. 1815 1816=item Time::Local 1817 1818The timelocal() and timegm() functions used to silently return bogus 1819results when the date fell outside the machine's integer range. They 1820now consistently croak() if the date falls in an unsupported range. 1821 1822=item Win32 1823 1824The error return value in list context has been changed for all functions 1825that return a list of values. Previously these functions returned a list 1826with a single element C<undef> if an error occurred. Now these functions 1827return the empty list in these situations. This applies to the following 1828functions: 1829 1830 Win32::FsType 1831 Win32::GetOSVersion 1832 1833The remaining functions are unchanged and continue to return C<undef> on 1834error even in list context. 1835 1836The Win32::SetLastError(ERROR) function has been added as a complement 1837to the Win32::GetLastError() function. 1838 1839The new Win32::GetFullPathName(FILENAME) returns the full absolute 1840pathname for FILENAME in scalar context. In list context it returns 1841a two-element list containing the fully qualified directory name and 1842the filename. See L<Win32>. 1843 1844=item XSLoader 1845 1846The XSLoader extension is a simpler alternative to DynaLoader. 1847See L<XSLoader>. 1848 1849=item DBM Filters 1850 1851A new feature called "DBM Filters" has been added to all the 1852DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File. 1853DBM Filters add four new methods to each DBM module: 1854 1855 filter_store_key 1856 filter_store_value 1857 filter_fetch_key 1858 filter_fetch_value 1859 1860These can be used to filter key-value pairs before the pairs are 1861written to the database or just after they are read from the database. 1862See L<perldbmfilter> for further information. 1863 1864=back 1865 1866=head2 Pragmata 1867 1868C<use attrs> is now obsolete, and is only provided for 1869backward-compatibility. It's been replaced by the C<sub : attributes> 1870syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>. 1871 1872Lexical warnings pragma, C<use warnings;>, to control optional warnings. 1873See L<perllexwarn>. 1874 1875C<use filetest> to control the behaviour of filetests (C<-r> C<-w> 1876...). Currently only one subpragma implemented, "use filetest 1877'access';", that uses access(2) or equivalent to check permissions 1878instead of using stat(2) as usual. This matters in filesystems 1879where there are ACLs (access control lists): the stat(2) might lie, 1880but access(2) knows better. 1881 1882The C<open> pragma can be used to specify default disciplines for 1883handle constructors (e.g. open()) and for qx//. The two 1884pseudo-disciplines C<:raw> and C<:crlf> are currently supported on 1885DOS-derivative platforms (i.e. where binmode is not a no-op). 1886See also L</"binmode() can be used to set :crlf and :raw modes">. 1887 1888=head1 Utility Changes 1889 1890=head2 dprofpp 1891 1892C<dprofpp> is used to display profile data generated using C<Devel::DProf>. 1893See L<dprofpp>. 1894 1895=head2 find2perl 1896 1897The C<find2perl> utility now uses the enhanced features of the File::Find 1898module. The -depth and -follow options are supported. Pod documentation 1899is also included in the script. 1900 1901=head2 h2xs 1902 1903The C<h2xs> tool can now work in conjunction with C<C::Scan> (available 1904from CPAN) to automatically parse real-life header files. The C<-M>, 1905C<-a>, C<-k>, and C<-o> options are new. 1906 1907=head2 perlcc 1908 1909C<perlcc> now supports the C and Bytecode backends. By default, 1910it generates output from the simple C backend rather than the 1911optimized C backend. 1912 1913Support for non-Unix platforms has been improved. 1914 1915=head2 perldoc 1916 1917C<perldoc> has been reworked to avoid possible security holes. 1918It will not by default let itself be run as the superuser, but you 1919may still use the B<-U> switch to try to make it drop privileges 1920first. 1921 1922=head2 The Perl Debugger 1923 1924Many bug fixes and enhancements were added to F<perl5db.pl>, the 1925Perl debugger. The help documentation was rearranged. New commands 1926include C<< < ? >>, C<< > ? >>, and C<< { ? >> to list out current 1927actions, C<man I<docpage>> to run your doc viewer on some perl 1928docset, and support for quoted options. The help information was 1929rearranged, and should be viewable once again if you're using B<less> 1930as your pager. A serious security hole was plugged--you should 1931immediately remove all older versions of the Perl debugger as 1932installed in previous releases, all the way back to perl3, from 1933your system to avoid being bitten by this. 1934 1935=head1 Improved Documentation 1936 1937Many of the platform-specific README files are now part of the perl 1938installation. See L<perl> for the complete list. 1939 1940=over 4 1941 1942=item perlapi.pod 1943 1944The official list of public Perl API functions. 1945 1946=item perlboot.pod 1947 1948A tutorial for beginners on object-oriented Perl. 1949 1950=item perlcompile.pod 1951 1952An introduction to using the Perl Compiler suite. 1953 1954=item perldbmfilter.pod 1955 1956A howto document on using the DBM filter facility. 1957 1958=item perldebug.pod 1959 1960All material unrelated to running the Perl debugger, plus all 1961low-level guts-like details that risked crushing the casual user 1962of the debugger, have been relocated from the old manpage to the 1963next entry below. 1964 1965=item perldebguts.pod 1966 1967This new manpage contains excessively low-level material not related 1968to the Perl debugger, but slightly related to debugging Perl itself. 1969It also contains some arcane internal details of how the debugging 1970process works that may only be of interest to developers of Perl 1971debuggers. 1972 1973=item perlfork.pod 1974 1975Notes on the fork() emulation currently available for the Windows platform. 1976 1977=item perlfilter.pod 1978 1979An introduction to writing Perl source filters. 1980 1981=item perlhack.pod 1982 1983Some guidelines for hacking the Perl source code. 1984 1985=item perlintern.pod 1986 1987A list of internal functions in the Perl source code. 1988(List is currently empty.) 1989 1990=item perllexwarn.pod 1991 1992Introduction and reference information about lexically scoped 1993warning categories. 1994 1995=item perlnumber.pod 1996 1997Detailed information about numbers as they are represented in Perl. 1998 1999=item perlopentut.pod 2000 2001A tutorial on using open() effectively. 2002 2003=item perlreftut.pod 2004 2005A tutorial that introduces the essentials of references. 2006 2007=item perltootc.pod 2008 2009A tutorial on managing class data for object modules. 2010 2011=item perltodo.pod 2012 2013Discussion of the most often wanted features that may someday be 2014supported in Perl. 2015 2016=item perlunicode.pod 2017 2018An introduction to Unicode support features in Perl. 2019 2020=back 2021 2022=head1 Performance enhancements 2023 2024=head2 Simple sort() using { $a <=> $b } and the like are optimized 2025 2026Many common sort() operations using a simple inlined block are now 2027optimized for faster performance. 2028 2029=head2 Optimized assignments to lexical variables 2030 2031Certain operations in the RHS of assignment statements have been 2032optimized to directly set the lexical variable on the LHS, 2033eliminating redundant copying overheads. 2034 2035=head2 Faster subroutine calls 2036 2037Minor changes in how subroutine calls are handled internally 2038provide marginal improvements in performance. 2039 2040=head2 delete(), each(), values() and hash iteration are faster 2041 2042The hash values returned by delete(), each(), values() and hashes in a 2043list context are the actual values in the hash, instead of copies. 2044This results in significantly better performance, because it eliminates 2045needless copying in most situations. 2046 2047=head1 Installation and Configuration Improvements 2048 2049=head2 -Dusethreads means something different 2050 2051The -Dusethreads flag now enables the experimental interpreter-based thread 2052support by default. To get the flavor of experimental threads that was in 20535.005 instead, you need to run Configure with "-Dusethreads -Duse5005threads". 2054 2055As of v5.6.0, interpreter-threads support is still lacking a way to 2056create new threads from Perl (i.e., C<use Thread;> will not work with 2057interpreter threads). C<use Thread;> continues to be available when you 2058specify the -Duse5005threads option to Configure, bugs and all. 2059 2060 NOTE: Support for threads continues to be an experimental feature. 2061 Interfaces and implementation are subject to sudden and drastic changes. 2062 2063=head2 New Configure flags 2064 2065The following new flags may be enabled on the Configure command line 2066by running Configure with C<-Dflag>. 2067 2068 usemultiplicity 2069 usethreads useithreads (new interpreter threads: no Perl API yet) 2070 usethreads use5005threads (threads as they were in 5.005) 2071 2072 use64bitint (equal to now deprecated 'use64bits') 2073 use64bitall 2074 2075 uselongdouble 2076 usemorebits 2077 uselargefiles 2078 usesocks (only SOCKS v5 supported) 2079 2080=head2 Threadedness and 64-bitness now more daring 2081 2082The Configure options enabling the use of threads and the use of 208364-bitness are now more daring in the sense that they no more have an 2084explicit list of operating systems of known threads/64-bit 2085capabilities. In other words: if your operating system has the 2086necessary APIs and datatypes, you should be able just to go ahead and 2087use them, for threads by Configure -Dusethreads, and for 64 bits 2088either explicitly by Configure -Duse64bitint or implicitly if your 2089system has 64-bit wide datatypes. See also L<"64-bit support">. 2090 2091=head2 Long Doubles 2092 2093Some platforms have "long doubles", floating point numbers of even 2094larger range than ordinary "doubles". To enable using long doubles for 2095Perl's scalars, use -Duselongdouble. 2096 2097=head2 -Dusemorebits 2098 2099You can enable both -Duse64bitint and -Duselongdouble with -Dusemorebits. 2100See also L<"64-bit support">. 2101 2102=head2 -Duselargefiles 2103 2104Some platforms support system APIs that are capable of handling large files 2105(typically, files larger than two gigabytes). Perl will try to use these 2106APIs if you ask for -Duselargefiles. 2107 2108See L<"Large file support"> for more information. 2109 2110=head2 installusrbinperl 2111 2112You can use "Configure -Uinstallusrbinperl" which causes installperl 2113to skip installing perl also as /usr/bin/perl. This is useful if you 2114prefer not to modify /usr/bin for some reason or another but harmful 2115because many scripts assume to find Perl in /usr/bin/perl. 2116 2117=head2 SOCKS support 2118 2119You can use "Configure -Dusesocks" which causes Perl to probe 2120for the SOCKS proxy protocol library (v5, not v4). For more information 2121on SOCKS, see: 2122 2123 http://www.socks.nec.com/ 2124 2125=head2 C<-A> flag 2126 2127You can "post-edit" the Configure variables using the Configure C<-A> 2128switch. The editing happens immediately after the platform specific 2129hints files have been processed but before the actual configuration 2130process starts. Run C<Configure -h> to find out the full C<-A> syntax. 2131 2132=head2 Enhanced Installation Directories 2133 2134The installation structure has been enriched to improve the support 2135for maintaining multiple versions of perl, to provide locations for 2136vendor-supplied modules, scripts, and manpages, and to ease maintenance 2137of locally-added modules, scripts, and manpages. See the section on 2138Installation Directories in the INSTALL file for complete details. 2139For most users building and installing from source, the defaults should 2140be fine. 2141 2142If you previously used C<Configure -Dsitelib> or C<-Dsitearch> to set 2143special values for library directories, you might wish to consider using 2144the new C<-Dsiteprefix> setting instead. Also, if you wish to re-use a 2145config.sh file from an earlier version of perl, you should be sure to 2146check that Configure makes sensible choices for the new directories. 2147See INSTALL for complete details. 2148 2149=head2 gcc automatically tried if 'cc' does not seem to be working 2150 2151In many platforms the vendor-supplied 'cc' is too stripped-down to 2152build Perl (basically, the 'cc' doesn't do ANSI C). If this seems 2153to be the case and the 'cc' does not seem to be the GNU C compiler 2154'gcc', an automatic attempt is made to find and use 'gcc' instead. 2155 2156=head1 Platform specific changes 2157 2158=head2 Supported platforms 2159 2160=over 4 2161 2162=item * 2163 2164The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread 2165extension. 2166 2167=item * 2168 2169GNU/Hurd is now supported. 2170 2171=item * 2172 2173Rhapsody/Darwin is now supported. 2174 2175=item * 2176 2177EPOC is now supported (on Psion 5). 2178 2179=item * 2180 2181The cygwin port (formerly cygwin32) has been greatly improved. 2182 2183=back 2184 2185=head2 DOS 2186 2187=over 4 2188 2189=item * 2190 2191Perl now works with djgpp 2.02 (and 2.03 alpha). 2192 2193=item * 2194 2195Environment variable names are not converted to uppercase any more. 2196 2197=item * 2198 2199Incorrect exit codes from backticks have been fixed. 2200 2201=item * 2202 2203This port continues to use its own builtin globbing (not File::Glob). 2204 2205=back 2206 2207=head2 OS390 (OpenEdition MVS) 2208 2209Support for this EBCDIC platform has not been renewed in this release. 2210There are difficulties in reconciling Perl's standardization on UTF-8 2211as its internal representation for characters with the EBCDIC character 2212set, because the two are incompatible. 2213 2214It is unclear whether future versions will renew support for this 2215platform, but the possibility exists. 2216 2217=head2 VMS 2218 2219Numerous revisions and extensions to configuration, build, testing, and 2220installation process to accommodate core changes and VMS-specific options. 2221 2222Expand %ENV-handling code to allow runtime mapping to logical names, 2223CLI symbols, and CRTL environ array. 2224 2225Extension of subprocess invocation code to accept filespecs as command 2226"verbs". 2227 2228Add to Perl command line processing the ability to use default file types and 2229to recognize Unix-style C<2E<gt>&1>. 2230 2231Expansion of File::Spec::VMS routines, and integration into ExtUtils::MM_VMS. 2232 2233Extension of ExtUtils::MM_VMS to handle complex extensions more flexibly. 2234 2235Barewords at start of Unix-syntax paths may be treated as text rather than 2236only as logical names. 2237 2238Optional secure translation of several logical names used internally by Perl. 2239 2240Miscellaneous bugfixing and porting of new core code to VMS. 2241 2242Thanks are gladly extended to the many people who have contributed VMS 2243patches, testing, and ideas. 2244 2245=head2 Win32 2246 2247Perl can now emulate fork() internally, using multiple interpreters running 2248in different concurrent threads. This support must be enabled at build 2249time. See L<perlfork> for detailed information. 2250 2251When given a pathname that consists only of a drivename, such as C<A:>, 2252opendir() and stat() now use the current working directory for the drive 2253rather than the drive root. 2254 2255The builtin XSUB functions in the Win32:: namespace are documented. See 2256L<Win32>. 2257 2258$^X now contains the full path name of the running executable. 2259 2260A Win32::GetLongPathName() function is provided to complement 2261Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>. 2262 2263POSIX::uname() is supported. 2264 2265system(1,...) now returns true process IDs rather than process 2266handles. kill() accepts any real process id, rather than strictly 2267return values from system(1,...). 2268 2269For better compatibility with Unix, C<kill(0, $pid)> can now be used to 2270test whether a process exists. 2271 2272The C<Shell> module is supported. 2273 2274Better support for building Perl under command.com in Windows 95 2275has been added. 2276 2277Scripts are read in binary mode by default to allow ByteLoader (and 2278the filter mechanism in general) to work properly. For compatibility, 2279the DATA filehandle will be set to text mode if a carriage return is 2280detected at the end of the line containing the __END__ or __DATA__ 2281token; if not, the DATA filehandle will be left open in binary mode. 2282Earlier versions always opened the DATA filehandle in text mode. 2283 2284The glob() operator is implemented via the C<File::Glob> extension, 2285which supports glob syntax of the C shell. This increases the flexibility 2286of the glob() operator, but there may be compatibility issues for 2287programs that relied on the older globbing syntax. If you want to 2288preserve compatibility with the older syntax, you might want to run 2289perl with C<-MFile::DosGlob>. For details and compatibility information, 2290see L<File::Glob>. 2291 2292=head1 Significant bug fixes 2293 2294=head2 <HANDLE> on empty files 2295 2296With C<$/> set to C<undef>, "slurping" an empty file returns a string of 2297zero length (instead of C<undef>, as it used to) the first time the 2298HANDLE is read after C<$/> is set to C<undef>. Further reads yield 2299C<undef>. 2300 2301This means that the following will append "foo" to an empty file (it used 2302to do nothing): 2303 2304 perl -0777 -pi -e 's/^/foo/' empty_file 2305 2306The behaviour of: 2307 2308 perl -pi -e 's/^/foo/' empty_file 2309 2310is unchanged (it continues to leave the file empty). 2311 2312=head2 C<eval '...'> improvements 2313 2314Line numbers (as reflected by caller() and most diagnostics) within 2315C<eval '...'> were often incorrect where here documents were involved. 2316This has been corrected. 2317 2318Lexical lookups for variables appearing in C<eval '...'> within 2319functions that were themselves called within an C<eval '...'> were 2320searching the wrong place for lexicals. The lexical search now 2321correctly ends at the subroutine's block boundary. 2322 2323The use of C<return> within C<eval {...}> caused $@ not to be reset 2324correctly when no exception occurred within the eval. This has 2325been fixed. 2326 2327Parsing of here documents used to be flawed when they appeared as 2328the replacement expression in C<eval 's/.../.../e'>. This has 2329been fixed. 2330 2331=head2 All compilation errors are true errors 2332 2333Some "errors" encountered at compile time were by necessity 2334generated as warnings followed by eventual termination of the 2335program. This enabled more such errors to be reported in a 2336single run, rather than causing a hard stop at the first error 2337that was encountered. 2338 2339The mechanism for reporting such errors has been reimplemented 2340to queue compile-time errors and report them at the end of the 2341compilation as true errors rather than as warnings. This fixes 2342cases where error messages leaked through in the form of warnings 2343when code was compiled at run time using C<eval STRING>, and 2344also allows such errors to be reliably trapped using C<eval "...">. 2345 2346=head2 Implicitly closed filehandles are safer 2347 2348Sometimes implicitly closed filehandles (as when they are localized, 2349and Perl automatically closes them on exiting the scope) could 2350inadvertently set $? or $!. This has been corrected. 2351 2352 2353=head2 Behavior of list slices is more consistent 2354 2355When taking a slice of a literal list (as opposed to a slice of 2356an array or hash), Perl used to return an empty list if the 2357result happened to be composed of all undef values. 2358 2359The new behavior is to produce an empty list if (and only if) 2360the original list was empty. Consider the following example: 2361 2362 @a = (1,undef,undef,2)[2,1,2]; 2363 2364The old behavior would have resulted in @a having no elements. 2365The new behavior ensures it has three undefined elements. 2366 2367Note in particular that the behavior of slices of the following 2368cases remains unchanged: 2369 2370 @a = ()[1,2]; 2371 @a = (getpwent)[7,0]; 2372 @a = (anything_returning_empty_list())[2,1,2]; 2373 @a = @b[2,1,2]; 2374 @a = @c{'a','b','c'}; 2375 2376See L<perldata>. 2377 2378=head2 C<(\$)> prototype and C<$foo{a}> 2379 2380A scalar reference prototype now correctly allows a hash or 2381array element in that slot. 2382 2383=head2 C<goto &sub> and AUTOLOAD 2384 2385The C<goto &sub> construct works correctly when C<&sub> happens 2386to be autoloaded. 2387 2388=head2 C<-bareword> allowed under C<use integer> 2389 2390The autoquoting of barewords preceded by C<-> did not work 2391in prior versions when the C<integer> pragma was enabled. 2392This has been fixed. 2393 2394=head2 Failures in DESTROY() 2395 2396When code in a destructor threw an exception, it went unnoticed 2397in earlier versions of Perl, unless someone happened to be 2398looking in $@ just after the point the destructor happened to 2399run. Such failures are now visible as warnings when warnings are 2400enabled. 2401 2402=head2 Locale bugs fixed 2403 2404printf() and sprintf() previously reset the numeric locale 2405back to the default "C" locale. This has been fixed. 2406 2407Numbers formatted according to the local numeric locale 2408(such as using a decimal comma instead of a decimal dot) caused 2409"isn't numeric" warnings, even while the operations accessing 2410those numbers produced correct results. These warnings have been 2411discontinued. 2412 2413=head2 Memory leaks 2414 2415The C<eval 'return sub {...}'> construct could sometimes leak 2416memory. This has been fixed. 2417 2418Operations that aren't filehandle constructors used to leak memory 2419when used on invalid filehandles. This has been fixed. 2420 2421Constructs that modified C<@_> could fail to deallocate values 2422in C<@_> and thus leak memory. This has been corrected. 2423 2424=head2 Spurious subroutine stubs after failed subroutine calls 2425 2426Perl could sometimes create empty subroutine stubs when a 2427subroutine was not found in the package. Such cases stopped 2428later method lookups from progressing into base packages. 2429This has been corrected. 2430 2431=head2 Taint failures under C<-U> 2432 2433When running in unsafe mode, taint violations could sometimes 2434cause silent failures. This has been fixed. 2435 2436=head2 END blocks and the C<-c> switch 2437 2438Prior versions used to run BEGIN B<and> END blocks when Perl was 2439run in compile-only mode. Since this is typically not the expected 2440behavior, END blocks are not executed anymore when the C<-c> switch 2441is used, or if compilation fails. 2442 2443See L</"Support for CHECK blocks"> for how to run things when the compile 2444phase ends. 2445 2446=head2 Potential to leak DATA filehandles 2447 2448Using the C<__DATA__> token creates an implicit filehandle to 2449the file that contains the token. It is the program's 2450responsibility to close it when it is done reading from it. 2451 2452This caveat is now better explained in the documentation. 2453See L<perldata>. 2454 2455=head1 New or Changed Diagnostics 2456 2457=over 4 2458 2459=item "%s" variable %s masks earlier declaration in same %s 2460 2461(W misc) A "my" or "our" variable has been redeclared in the current scope or statement, 2462effectively eliminating all access to the previous instance. This is almost 2463always a typographical error. Note that the earlier variable will still exist 2464until the end of the scope or until all closure referents to it are 2465destroyed. 2466 2467=item "my sub" not yet implemented 2468 2469(F) Lexically scoped subroutines are not yet implemented. Don't try that 2470yet. 2471 2472=item "our" variable %s redeclared 2473 2474(W misc) You seem to have already declared the same global once before in the 2475current lexical scope. 2476 2477=item '!' allowed only after types %s 2478 2479(F) The '!' is allowed in pack() and unpack() only after certain types. 2480See L<perlfunc/pack>. 2481 2482=item / cannot take a count 2483 2484(F) You had an unpack template indicating a counted-length string, 2485but you have also specified an explicit size for the string. 2486See L<perlfunc/pack>. 2487 2488=item / must be followed by a, A or Z 2489 2490(F) You had an unpack template indicating a counted-length string, 2491which must be followed by one of the letters a, A or Z 2492to indicate what sort of string is to be unpacked. 2493See L<perlfunc/pack>. 2494 2495=item / must be followed by a*, A* or Z* 2496 2497(F) You had a pack template indicating a counted-length string, 2498Currently the only things that can have their length counted are a*, A* or Z*. 2499See L<perlfunc/pack>. 2500 2501=item / must follow a numeric type 2502 2503(F) You had an unpack template that contained a '#', 2504but this did not follow some numeric unpack specification. 2505See L<perlfunc/pack>. 2506 2507=item /%s/: Unrecognized escape \\%c passed through 2508 2509(W regexp) You used a backslash-character combination which is not recognized 2510by Perl. This combination appears in an interpolated variable or a 2511C<'>-delimited regular expression. The character was understood literally. 2512 2513=item /%s/: Unrecognized escape \\%c in character class passed through 2514 2515(W regexp) You used a backslash-character combination which is not recognized 2516by Perl inside character classes. The character was understood literally. 2517 2518=item /%s/ should probably be written as "%s" 2519 2520(W syntax) You have used a pattern where Perl expected to find a string, 2521as in the first argument to C<join>. Perl will treat the true 2522or false result of matching the pattern against $_ as the string, 2523which is probably not what you had in mind. 2524 2525=item %s() called too early to check prototype 2526 2527(W prototype) You've called a function that has a prototype before the parser saw a 2528definition or declaration for it, and Perl could not check that the call 2529conforms to the prototype. You need to either add an early prototype 2530declaration for the subroutine in question, or move the subroutine 2531definition ahead of the call to get proper prototype checking. Alternatively, 2532if you are certain that you're calling the function correctly, you may put 2533an ampersand before the name to avoid the warning. See L<perlsub>. 2534 2535=item %s argument is not a HASH or ARRAY element 2536 2537(F) The argument to exists() must be a hash or array element, such as: 2538 2539 $foo{$bar} 2540 $ref->{"susie"}[12] 2541 2542=item %s argument is not a HASH or ARRAY element or slice 2543 2544(F) The argument to delete() must be either a hash or array element, such as: 2545 2546 $foo{$bar} 2547 $ref->{"susie"}[12] 2548 2549or a hash or array slice, such as: 2550 2551 @foo[$bar, $baz, $xyzzy] 2552 @{$ref->[12]}{"susie", "queue"} 2553 2554=item %s argument is not a subroutine name 2555 2556(F) The argument to exists() for C<exists &sub> must be a subroutine 2557name, and not a subroutine call. C<exists &sub()> will generate this error. 2558 2559=item %s package attribute may clash with future reserved word: %s 2560 2561(W reserved) A lowercase attribute name was used that had a package-specific handler. 2562That name might have a meaning to Perl itself some day, even though it 2563doesn't yet. Perhaps you should use a mixed-case attribute name, instead. 2564See L<attributes>. 2565 2566=item (in cleanup) %s 2567 2568(W misc) This prefix usually indicates that a DESTROY() method raised 2569the indicated exception. Since destructors are usually called by 2570the system at arbitrary points during execution, and often a vast 2571number of times, the warning is issued only once for any number 2572of failures that would otherwise result in the same message being 2573repeated. 2574 2575Failure of user callbacks dispatched using the C<G_KEEPERR> flag 2576could also result in this warning. See L<perlcall/G_KEEPERR>. 2577 2578=item <> should be quotes 2579 2580(F) You wrote C<< require <file> >> when you should have written 2581C<require 'file'>. 2582 2583=item Attempt to join self 2584 2585(F) You tried to join a thread from within itself, which is an 2586impossible task. You may be joining the wrong thread, or you may 2587need to move the join() to some other thread. 2588 2589=item Bad evalled substitution pattern 2590 2591(F) You've used the /e switch to evaluate the replacement for a 2592substitution, but perl found a syntax error in the code to evaluate, 2593most likely an unexpected right brace '}'. 2594 2595=item Bad realloc() ignored 2596 2597(S) An internal routine called realloc() on something that had never been 2598malloc()ed in the first place. Mandatory, but can be disabled by 2599setting environment variable C<PERL_BADFREE> to 1. 2600 2601=item Bareword found in conditional 2602 2603(W bareword) The compiler found a bareword where it expected a conditional, 2604which often indicates that an || or && was parsed as part of the 2605last argument of the previous construct, for example: 2606 2607 open FOO || die; 2608 2609It may also indicate a misspelled constant that has been interpreted 2610as a bareword: 2611 2612 use constant TYPO => 1; 2613 if (TYOP) { print "foo" } 2614 2615The C<strict> pragma is useful in avoiding such errors. 2616 2617=item Binary number > 0b11111111111111111111111111111111 non-portable 2618 2619(W portable) The binary number you specified is larger than 2**32-1 2620(4294967295) and therefore non-portable between systems. See 2621L<perlport> for more on portability concerns. 2622 2623=item Bit vector size > 32 non-portable 2624 2625(W portable) Using bit vector sizes larger than 32 is non-portable. 2626 2627=item Buffer overflow in prime_env_iter: %s 2628 2629(W internal) A warning peculiar to VMS. While Perl was preparing to iterate over 2630%ENV, it encountered a logical name or symbol definition which was too long, 2631so it was truncated to the string shown. 2632 2633=item Can't check filesystem of script "%s" 2634 2635(P) For some reason you can't check the filesystem of the script for nosuid. 2636 2637=item Can't declare class for non-scalar %s in "%s" 2638 2639(S) Currently, only scalar variables can declared with a specific class 2640qualifier in a "my" or "our" declaration. The semantics may be extended 2641for other types of variables in future. 2642 2643=item Can't declare %s in "%s" 2644 2645(F) Only scalar, array, and hash variables may be declared as "my" or 2646"our" variables. They must have ordinary identifiers as names. 2647 2648=item Can't ignore signal CHLD, forcing to default 2649 2650(W signal) Perl has detected that it is being run with the SIGCHLD signal 2651(sometimes known as SIGCLD) disabled. Since disabling this signal 2652will interfere with proper determination of exit status of child 2653processes, Perl has reset the signal to its default value. 2654This situation typically indicates that the parent program under 2655which Perl may be running (e.g., cron) is being very careless. 2656 2657=item Can't modify non-lvalue subroutine call 2658 2659(F) Subroutines meant to be used in lvalue context should be declared as 2660such, see L<perlsub/"Lvalue subroutines">. 2661 2662=item Can't read CRTL environ 2663 2664(S) A warning peculiar to VMS. Perl tried to read an element of %ENV 2665from the CRTL's internal environment array and discovered the array was 2666missing. You need to figure out where your CRTL misplaced its environ 2667or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched. 2668 2669=item Can't remove %s: %s, skipping file 2670 2671(S) You requested an inplace edit without creating a backup file. Perl 2672was unable to remove the original file to replace it with the modified 2673file. The file was left unmodified. 2674 2675=item Can't return %s from lvalue subroutine 2676 2677(F) Perl detected an attempt to return illegal lvalues (such 2678as temporary or readonly values) from a subroutine used as an lvalue. 2679This is not allowed. 2680 2681=item Can't weaken a nonreference 2682 2683(F) You attempted to weaken something that was not a reference. Only 2684references can be weakened. 2685 2686=item Character class [:%s:] unknown 2687 2688(F) The class in the character class [: :] syntax is unknown. 2689See L<perlre>. 2690 2691=item Character class syntax [%s] belongs inside character classes 2692 2693(W unsafe) The character class constructs [: :], [= =], and [. .] go 2694I<inside> character classes, the [] are part of the construct, 2695for example: /[012[:alpha:]345]/. Note that [= =] and [. .] 2696are not currently implemented; they are simply placeholders for 2697future extensions. 2698 2699=item Constant is not %s reference 2700 2701(F) A constant value (perhaps declared using the C<use constant> pragma) 2702is being dereferenced, but it amounts to the wrong type of reference. The 2703message indicates the type of reference that was expected. This usually 2704indicates a syntax error in dereferencing the constant value. 2705See L<perlsub/"Constant Functions"> and L<constant>. 2706 2707=item constant(%s): %s 2708 2709(F) The parser found inconsistencies either while attempting to define an 2710overloaded constant, or when trying to find the character name specified 2711in the C<\N{...}> escape. Perhaps you forgot to load the corresponding 2712C<overload> or C<charnames> pragma? See L<charnames> and L<overload>. 2713 2714=item CORE::%s is not a keyword 2715 2716(F) The CORE:: namespace is reserved for Perl keywords. 2717 2718=item defined(@array) is deprecated 2719 2720(D) defined() is not usually useful on arrays because it checks for an 2721undefined I<scalar> value. If you want to see if the array is empty, 2722just use C<if (@array) { # not empty }> for example. 2723 2724=item defined(%hash) is deprecated 2725 2726(D) defined() is not usually useful on hashes because it checks for an 2727undefined I<scalar> value. If you want to see if the hash is empty, 2728just use C<if (%hash) { # not empty }> for example. 2729 2730=item Did not produce a valid header 2731 2732See Server error. 2733 2734=item (Did you mean "local" instead of "our"?) 2735 2736(W misc) Remember that "our" does not localize the declared global variable. 2737You have declared it again in the same lexical scope, which seems superfluous. 2738 2739=item Document contains no data 2740 2741See Server error. 2742 2743=item entering effective %s failed 2744 2745(F) While under the C<use filetest> pragma, switching the real and 2746effective uids or gids failed. 2747 2748=item false [] range "%s" in regexp 2749 2750(W regexp) A character class range must start and end at a literal character, not 2751another character class like C<\d> or C<[:alpha:]>. The "-" in your false 2752range is interpreted as a literal "-". Consider quoting the "-", "\-". 2753See L<perlre>. 2754 2755=item Filehandle %s opened only for output 2756 2757(W io) You tried to read from a filehandle opened only for writing. If you 2758intended it to be a read/write filehandle, you needed to open it with 2759"+<" or "+>" or "+>>" instead of with "<" or nothing. If 2760you intended only to read from the file, use "<". See 2761L<perlfunc/open>. 2762 2763=item flock() on closed filehandle %s 2764 2765(W closed) The filehandle you're attempting to flock() got itself closed some 2766time before now. Check your logic flow. flock() operates on filehandles. 2767Are you attempting to call flock() on a dirhandle by the same name? 2768 2769=item Global symbol "%s" requires explicit package name 2770 2771(F) You've said "use strict vars", which indicates that all variables 2772must either be lexically scoped (using "my"), declared beforehand using 2773"our", or explicitly qualified to say which package the global variable 2774is in (using "::"). 2775 2776=item Hexadecimal number > 0xffffffff non-portable 2777 2778(W portable) The hexadecimal number you specified is larger than 2**32-1 2779(4294967295) and therefore non-portable between systems. See 2780L<perlport> for more on portability concerns. 2781 2782=item Ill-formed CRTL environ value "%s" 2783 2784(W internal) A warning peculiar to VMS. Perl tried to read the CRTL's internal 2785environ array, and encountered an element without the C<=> delimiter 2786used to separate keys from values. The element is ignored. 2787 2788=item Ill-formed message in prime_env_iter: |%s| 2789 2790(W internal) A warning peculiar to VMS. Perl tried to read a logical name 2791or CLI symbol definition when preparing to iterate over %ENV, and 2792didn't see the expected delimiter between key and value, so the 2793line was ignored. 2794 2795=item Illegal binary digit %s 2796 2797(F) You used a digit other than 0 or 1 in a binary number. 2798 2799=item Illegal binary digit %s ignored 2800 2801(W digit) You may have tried to use a digit other than 0 or 1 in a binary number. 2802Interpretation of the binary number stopped before the offending digit. 2803 2804=item Illegal number of bits in vec 2805 2806(F) The number of bits in vec() (the third argument) must be a power of 2807two from 1 to 32 (or 64, if your platform supports that). 2808 2809=item Integer overflow in %s number 2810 2811(W overflow) The hexadecimal, octal or binary number you have specified either 2812as a literal or as an argument to hex() or oct() is too big for your 2813architecture, and has been converted to a floating point number. On a 281432-bit architecture the largest hexadecimal, octal or binary number 2815representable without overflow is 0xFFFFFFFF, 037777777777, or 28160b11111111111111111111111111111111 respectively. Note that Perl 2817transparently promotes all numbers to a floating point representation 2818internally--subject to loss of precision errors in subsequent 2819operations. 2820 2821=item Invalid %s attribute: %s 2822 2823The indicated attribute for a subroutine or variable was not recognized 2824by Perl or by a user-supplied handler. See L<attributes>. 2825 2826=item Invalid %s attributes: %s 2827 2828The indicated attributes for a subroutine or variable were not recognized 2829by Perl or by a user-supplied handler. See L<attributes>. 2830 2831=item invalid [] range "%s" in regexp 2832 2833The offending range is now explicitly displayed. 2834 2835=item Invalid separator character %s in attribute list 2836 2837(F) Something other than a colon or whitespace was seen between the 2838elements of an attribute list. If the previous attribute 2839had a parenthesised parameter list, perhaps that list was terminated 2840too soon. See L<attributes>. 2841 2842=item Invalid separator character %s in subroutine attribute list 2843 2844(F) Something other than a colon or whitespace was seen between the 2845elements of a subroutine attribute list. If the previous attribute 2846had a parenthesised parameter list, perhaps that list was terminated 2847too soon. 2848 2849=item leaving effective %s failed 2850 2851(F) While under the C<use filetest> pragma, switching the real and 2852effective uids or gids failed. 2853 2854=item Lvalue subs returning %s not implemented yet 2855 2856(F) Due to limitations in the current implementation, array and hash 2857values cannot be returned in subroutines used in lvalue context. 2858See L<perlsub/"Lvalue subroutines">. 2859 2860=item Method %s not permitted 2861 2862See Server error. 2863 2864=item Missing %sbrace%s on \N{} 2865 2866(F) Wrong syntax of character name literal C<\N{charname}> within 2867double-quotish context. 2868 2869=item Missing command in piped open 2870 2871(W pipe) You used the C<open(FH, "| command")> or C<open(FH, "command |")> 2872construction, but the command was missing or blank. 2873 2874=item Missing name in "my sub" 2875 2876(F) The reserved syntax for lexically scoped subroutines requires that they 2877have a name with which they can be found. 2878 2879=item No %s specified for -%c 2880 2881(F) The indicated command line switch needs a mandatory argument, but 2882you haven't specified one. 2883 2884=item No package name allowed for variable %s in "our" 2885 2886(F) Fully qualified variable names are not allowed in "our" declarations, 2887because that doesn't make much sense under existing semantics. Such 2888syntax is reserved for future extensions. 2889 2890=item No space allowed after -%c 2891 2892(F) The argument to the indicated command line switch must follow immediately 2893after the switch, without intervening spaces. 2894 2895=item no UTC offset information; assuming local time is UTC 2896 2897(S) A warning peculiar to VMS. Perl was unable to find the local 2898timezone offset, so it's assuming that local system time is equivalent 2899to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL> 2900to translate to the number of seconds which need to be added to UTC to 2901get local time. 2902 2903=item Octal number > 037777777777 non-portable 2904 2905(W portable) The octal number you specified is larger than 2**32-1 (4294967295) 2906and therefore non-portable between systems. See L<perlport> for more 2907on portability concerns. 2908 2909See also L<perlport> for writing portable code. 2910 2911=item panic: del_backref 2912 2913(P) Failed an internal consistency check while trying to reset a weak 2914reference. 2915 2916=item panic: kid popen errno read 2917 2918(F) forked child returned an incomprehensible message about its errno. 2919 2920=item panic: magic_killbackrefs 2921 2922(P) Failed an internal consistency check while trying to reset all weak 2923references to an object. 2924 2925=item Parentheses missing around "%s" list 2926 2927(W parenthesis) You said something like 2928 2929 my $foo, $bar = @_; 2930 2931when you meant 2932 2933 my ($foo, $bar) = @_; 2934 2935Remember that "my", "our", and "local" bind tighter than comma. 2936 2937=item Possible unintended interpolation of %s in string 2938 2939(W ambiguous) It used to be that Perl would try to guess whether you 2940wanted an array interpolated or a literal @. It no longer does this; 2941arrays are now I<always> interpolated into strings. This means that 2942if you try something like: 2943 2944 print "fred@example.com"; 2945 2946and the array C<@example> doesn't exist, Perl is going to print 2947C<fred.com>, which is probably not what you wanted. To get a literal 2948C<@> sign in a string, put a backslash before it, just as you would 2949to get a literal C<$> sign. 2950 2951=item Possible Y2K bug: %s 2952 2953(W y2k) You are concatenating the number 19 with another number, which 2954could be a potential Year 2000 problem. 2955 2956=item pragma "attrs" is deprecated, use "sub NAME : ATTRS" instead 2957 2958(W deprecated) You have written something like this: 2959 2960 sub doit 2961 { 2962 use attrs qw(locked); 2963 } 2964 2965You should use the new declaration syntax instead. 2966 2967 sub doit : locked 2968 { 2969 ... 2970 2971The C<use attrs> pragma is now obsolete, and is only provided for 2972backward-compatibility. See L<perlsub/"Subroutine Attributes">. 2973 2974 2975=item Premature end of script headers 2976 2977See Server error. 2978 2979=item Repeat count in pack overflows 2980 2981(F) You can't specify a repeat count so large that it overflows 2982your signed integers. See L<perlfunc/pack>. 2983 2984=item Repeat count in unpack overflows 2985 2986(F) You can't specify a repeat count so large that it overflows 2987your signed integers. See L<perlfunc/unpack>. 2988 2989=item realloc() of freed memory ignored 2990 2991(S) An internal routine called realloc() on something that had already 2992been freed. 2993 2994=item Reference is already weak 2995 2996(W misc) You have attempted to weaken a reference that is already weak. 2997Doing so has no effect. 2998 2999=item setpgrp can't take arguments 3000 3001(F) Your system has the setpgrp() from BSD 4.2, which takes no arguments, 3002unlike POSIX setpgid(), which takes a process ID and process group ID. 3003 3004=item Strange *+?{} on zero-length expression 3005 3006(W regexp) You applied a regular expression quantifier in a place where it 3007makes no sense, such as on a zero-width assertion. 3008Try putting the quantifier inside the assertion instead. For example, 3009the way to match "abc" provided that it is followed by three 3010repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>. 3011 3012=item switching effective %s is not implemented 3013 3014(F) While under the C<use filetest> pragma, we cannot switch the 3015real and effective uids or gids. 3016 3017=item This Perl can't reset CRTL environ elements (%s) 3018 3019=item This Perl can't set CRTL environ elements (%s=%s) 3020 3021(W internal) Warnings peculiar to VMS. You tried to change or delete an element 3022of the CRTL's internal environ array, but your copy of Perl wasn't 3023built with a CRTL that contained the setenv() function. You'll need to 3024rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see 3025L<perlvms>) so that the environ array isn't the target of the change to 3026%ENV which produced the warning. 3027 3028=item Too late to run %s block 3029 3030(W void) A CHECK or INIT block is being defined during run time proper, 3031when the opportunity to run them has already passed. Perhaps you are 3032loading a file with C<require> or C<do> when you should be using 3033C<use> instead. Or perhaps you should put the C<require> or C<do> 3034inside a BEGIN block. 3035 3036=item Unknown open() mode '%s' 3037 3038(F) The second argument of 3-argument open() is not among the list 3039of valid modes: C<< < >>, C<< > >>, C<<< >> >>>, C<< +< >>, 3040C<< +> >>, C<<< +>> >>>, C<-|>, C<|->. 3041 3042=item Unknown process %x sent message to prime_env_iter: %s 3043 3044(P) An error peculiar to VMS. Perl was reading values for %ENV before 3045iterating over it, and someone else stuck a message in the stream of 3046data Perl expected. Someone's very confused, or perhaps trying to 3047subvert Perl's population of %ENV for nefarious purposes. 3048 3049=item Unrecognized escape \\%c passed through 3050 3051(W misc) You used a backslash-character combination which is not recognized 3052by Perl. The character was understood literally. 3053 3054=item Unterminated attribute parameter in attribute list 3055 3056(F) The lexer saw an opening (left) parenthesis character while parsing an 3057attribute list, but the matching closing (right) parenthesis 3058character was not found. You may need to add (or remove) a backslash 3059character to get your parentheses to balance. See L<attributes>. 3060 3061=item Unterminated attribute list 3062 3063(F) The lexer found something other than a simple identifier at the start 3064of an attribute, and it wasn't a semicolon or the start of a 3065block. Perhaps you terminated the parameter list of the previous attribute 3066too soon. See L<attributes>. 3067 3068=item Unterminated attribute parameter in subroutine attribute list 3069 3070(F) The lexer saw an opening (left) parenthesis character while parsing a 3071subroutine attribute list, but the matching closing (right) parenthesis 3072character was not found. You may need to add (or remove) a backslash 3073character to get your parentheses to balance. 3074 3075=item Unterminated subroutine attribute list 3076 3077(F) The lexer found something other than a simple identifier at the start 3078of a subroutine attribute, and it wasn't a semicolon or the start of a 3079block. Perhaps you terminated the parameter list of the previous attribute 3080too soon. 3081 3082=item Value of CLI symbol "%s" too long 3083 3084(W misc) A warning peculiar to VMS. Perl tried to read the value of an %ENV 3085element from a CLI symbol table, and found a resultant string longer 3086than 1024 characters. The return value has been truncated to 1024 3087characters. 3088 3089=item Version number must be a constant number 3090 3091(P) The attempt to translate a C<use Module n.n LIST> statement into 3092its equivalent C<BEGIN> block found an internal inconsistency with 3093the version number. 3094 3095=back 3096 3097=head1 New tests 3098 3099=over 4 3100 3101=item lib/attrs 3102 3103Compatibility tests for C<sub : attrs> vs the older C<use attrs>. 3104 3105=item lib/env 3106 3107Tests for new environment scalar capability (e.g., C<use Env qw($BAR);>). 3108 3109=item lib/env-array 3110 3111Tests for new environment array capability (e.g., C<use Env qw(@PATH);>). 3112 3113=item lib/io_const 3114 3115IO constants (SEEK_*, _IO*). 3116 3117=item lib/io_dir 3118 3119Directory-related IO methods (new, read, close, rewind, tied delete). 3120 3121=item lib/io_multihomed 3122 3123INET sockets with multi-homed hosts. 3124 3125=item lib/io_poll 3126 3127IO poll(). 3128 3129=item lib/io_unix 3130 3131UNIX sockets. 3132 3133=item op/attrs 3134 3135Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>. 3136 3137=item op/filetest 3138 3139File test operators. 3140 3141=item op/lex_assign 3142 3143Verify operations that access pad objects (lexicals and temporaries). 3144 3145=item op/exists_sub 3146 3147Verify C<exists &sub> operations. 3148 3149=back 3150 3151=head1 Incompatible Changes 3152 3153=head2 Perl Source Incompatibilities 3154 3155Beware that any new warnings that have been added or old ones 3156that have been enhanced are B<not> considered incompatible changes. 3157 3158Since all new warnings must be explicitly requested via the C<-w> 3159switch or the C<warnings> pragma, it is ultimately the programmer's 3160responsibility to ensure that warnings are enabled judiciously. 3161 3162=over 4 3163 3164=item CHECK is a new keyword 3165 3166All subroutine definitions named CHECK are now special. See 3167C</"Support for CHECK blocks"> for more information. 3168 3169=item Treatment of list slices of undef has changed 3170 3171There is a potential incompatibility in the behavior of list slices 3172that are comprised entirely of undefined values. 3173See L</"Behavior of list slices is more consistent">. 3174 3175=item Format of $English::PERL_VERSION is different 3176 3177The English module now sets $PERL_VERSION to $^V (a string value) rather 3178than C<$]> (a numeric value). This is a potential incompatibility. 3179Send us a report via perlbug if you are affected by this. 3180 3181See L</"Improved Perl version numbering system"> for the reasons for 3182this change. 3183 3184=item Literals of the form C<1.2.3> parse differently 3185 3186Previously, numeric literals with more than one dot in them were 3187interpreted as a floating point number concatenated with one or more 3188numbers. Such "numbers" are now parsed as strings composed of the 3189specified ordinals. 3190 3191For example, C<print 97.98.99> used to output C<97.9899> in earlier 3192versions, but now prints C<abc>. 3193 3194See L</"Support for strings represented as a vector of ordinals">. 3195 3196=item Possibly changed pseudo-random number generator 3197 3198Perl programs that depend on reproducing a specific set of pseudo-random 3199numbers may now produce different output due to improvements made to the 3200rand() builtin. You can use C<sh Configure -Drandfunc=rand> to obtain 3201the old behavior. 3202 3203See L</"Better pseudo-random number generator">. 3204 3205=item Hashing function for hash keys has changed 3206 3207Even though Perl hashes are not order preserving, the apparently 3208random order encountered when iterating on the contents of a hash 3209is actually determined by the hashing algorithm used. Improvements 3210in the algorithm may yield a random order that is B<different> from 3211that of previous versions, especially when iterating on hashes. 3212 3213See L</"Better worst-case behavior of hashes"> for additional 3214information. 3215 3216=item C<undef> fails on read only values 3217 3218Using the C<undef> operator on a readonly value (such as $1) has 3219the same effect as assigning C<undef> to the readonly value--it 3220throws an exception. 3221 3222=item Close-on-exec bit may be set on pipe and socket handles 3223 3224Pipe and socket handles are also now subject to the close-on-exec 3225behavior determined by the special variable $^F. 3226 3227See L</"More consistent close-on-exec behavior">. 3228 3229=item Writing C<"$$1"> to mean C<"${$}1"> is unsupported 3230 3231Perl 5.004 deprecated the interpretation of C<$$1> and 3232similar within interpolated strings to mean C<$$ . "1">, 3233but still allowed it. 3234 3235In Perl 5.6.0 and later, C<"$$1"> always means C<"${$1}">. 3236 3237=item delete(), each(), values() and C<\(%h)> 3238 3239operate on aliases to values, not copies 3240 3241delete(), each(), values() and hashes (e.g. C<\(%h)>) 3242in a list context return the actual 3243values in the hash, instead of copies (as they used to in earlier 3244versions). Typical idioms for using these constructs copy the 3245returned values, but this can make a significant difference when 3246creating references to the returned values. Keys in the hash are still 3247returned as copies when iterating on a hash. 3248 3249See also L</"delete(), each(), values() and hash iteration are faster">. 3250 3251=item vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS 3252 3253vec() generates a run-time error if the BITS argument is not 3254a valid power-of-two integer. 3255 3256=item Text of some diagnostic output has changed 3257 3258Most references to internal Perl operations in diagnostics 3259have been changed to be more descriptive. This may be an 3260issue for programs that may incorrectly rely on the exact 3261text of diagnostics for proper functioning. 3262 3263=item C<%@> has been removed 3264 3265The undocumented special variable C<%@> that used to accumulate 3266"background" errors (such as those that happen in DESTROY()) 3267has been removed, because it could potentially result in memory 3268leaks. 3269 3270=item Parenthesized not() behaves like a list operator 3271 3272The C<not> operator now falls under the "if it looks like a function, 3273it behaves like a function" rule. 3274 3275As a result, the parenthesized form can be used with C<grep> and C<map>. 3276The following construct used to be a syntax error before, but it works 3277as expected now: 3278 3279 grep not($_), @things; 3280 3281On the other hand, using C<not> with a literal list slice may not 3282work. The following previously allowed construct: 3283 3284 print not (1,2,3)[0]; 3285 3286needs to be written with additional parentheses now: 3287 3288 print not((1,2,3)[0]); 3289 3290The behavior remains unaffected when C<not> is not followed by parentheses. 3291 3292=item Semantics of bareword prototype C<(*)> have changed 3293 3294The semantics of the bareword prototype C<*> have changed. Perl 5.005 3295always coerced simple scalar arguments to a typeglob, which wasn't useful 3296in situations where the subroutine must distinguish between a simple 3297scalar and a typeglob. The new behavior is to not coerce bareword 3298arguments to a typeglob. The value will always be visible as either 3299a simple scalar or as a reference to a typeglob. 3300 3301See L</"More functional bareword prototype (*)">. 3302 3303=item Semantics of bit operators may have changed on 64-bit platforms 3304 3305If your platform is either natively 64-bit or if Perl has been 3306configured to used 64-bit integers, i.e., $Config{ivsize} is 8, 3307there may be a potential incompatibility in the behavior of bitwise 3308numeric operators (& | ^ ~ << >>). These operators used to strictly 3309operate on the lower 32 bits of integers in previous versions, but now 3310operate over the entire native integral width. In particular, note 3311that unary C<~> will produce different results on platforms that have 3312different $Config{ivsize}. For portability, be sure to mask off 3313the excess bits in the result of unary C<~>, e.g., C<~$x & 0xffffffff>. 3314 3315See L</"Bit operators support full native integer width">. 3316 3317=item More builtins taint their results 3318 3319As described in L</"Improved security features">, there may be more 3320sources of taint in a Perl program. 3321 3322To avoid these new tainting behaviors, you can build Perl with the 3323Configure option C<-Accflags=-DINCOMPLETE_TAINTS>. Beware that the 3324ensuing perl binary may be insecure. 3325 3326=back 3327 3328=head2 C Source Incompatibilities 3329 3330=over 4 3331 3332=item C<PERL_POLLUTE> 3333 3334Release 5.005 grandfathered old global symbol names by providing preprocessor 3335macros for extension source compatibility. As of release 5.6.0, these 3336preprocessor definitions are not available by default. You need to explicitly 3337compile perl with C<-DPERL_POLLUTE> to get these definitions. For 3338extensions still using the old symbols, this option can be 3339specified via MakeMaker: 3340 3341 perl Makefile.PL POLLUTE=1 3342 3343=item C<PERL_IMPLICIT_CONTEXT> 3344 3345This new build option provides a set of macros for all API functions 3346such that an implicit interpreter/thread context argument is passed to 3347every API function. As a result of this, something like C<sv_setsv(foo,bar)> 3348amounts to a macro invocation that actually translates to something like 3349C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected 3350to not have any significant source compatibility issues, the difference 3351between a macro and a real function call will need to be considered. 3352 3353This means that there B<is> a source compatibility issue as a result of 3354this if your extensions attempt to use pointers to any of the Perl API 3355functions. 3356 3357Note that the above issue is not relevant to the default build of 3358Perl, whose interfaces continue to match those of prior versions 3359(but subject to the other options described here). 3360 3361See L<perlguts/"The Perl API"> for detailed information on the 3362ramifications of building Perl with this option. 3363 3364 NOTE: PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built 3365 with one of -Dusethreads, -Dusemultiplicity, or both. It is not 3366 intended to be enabled by users at this time. 3367 3368=item C<PERL_POLLUTE_MALLOC> 3369 3370Enabling Perl's malloc in release 5.005 and earlier caused the namespace of 3371the system's malloc family of functions to be usurped by the Perl versions, 3372since by default they used the same names. Besides causing problems on 3373platforms that do not allow these functions to be cleanly replaced, this 3374also meant that the system versions could not be called in programs that 3375used Perl's malloc. Previous versions of Perl have allowed this behaviour 3376to be suppressed with the HIDEMYMALLOC and EMBEDMYMALLOC preprocessor 3377definitions. 3378 3379As of release 5.6.0, Perl's malloc family of functions have default names 3380distinct from the system versions. You need to explicitly compile perl with 3381C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC 3382and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now 3383the default. 3384 3385Note that these functions do B<not> constitute Perl's memory allocation API. 3386See L<perlguts/"Memory Allocation"> for further information about that. 3387 3388=back 3389 3390=head2 Compatible C Source API Changes 3391 3392=over 4 3393 3394=item C<PATCHLEVEL> is now C<PERL_VERSION> 3395 3396The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION> 3397are now available by default from perl.h, and reflect the base revision, 3398patchlevel, and subversion respectively. C<PERL_REVISION> had no 3399prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were 3400previously available as C<PATCHLEVEL> and C<SUBVERSION>. 3401 3402The new names cause less pollution of the B<cpp> namespace and reflect what 3403the numbers have come to stand for in common practice. For compatibility, 3404the old names are still supported when F<patchlevel.h> is explicitly 3405included (as required before), so there is no source incompatibility 3406from the change. 3407 3408=back 3409 3410=head2 Binary Incompatibilities 3411 3412In general, the default build of this release is expected to be binary 3413compatible for extensions built with the 5.005 release or its maintenance 3414versions. However, specific platforms may have broken binary compatibility 3415due to changes in the defaults used in hints files. Therefore, please be 3416sure to always check the platform-specific README files for any notes to 3417the contrary. 3418 3419The usethreads or usemultiplicity builds are B<not> binary compatible 3420with the corresponding builds in 5.005. 3421 3422On platforms that require an explicit list of exports (AIX, OS/2 and Windows, 3423among others), purely internal symbols such as parser functions and the 3424run time opcodes are not exported by default. Perl 5.005 used to export 3425all functions irrespective of whether they were considered part of the 3426public API or not. 3427 3428For the full list of public API functions, see L<perlapi>. 3429 3430=head1 Known Problems 3431 3432=head2 Localizing a tied hash element may leak memory 3433 3434As of the 5.6.1 release, there is a known leak when code such as this 3435is executed: 3436 3437 use Tie::Hash; 3438 tie my %tie_hash => 'Tie::StdHash'; 3439 3440 ... 3441 3442 local($tie_hash{Foo}) = 1; # leaks 3443 3444=head2 Known test failures 3445 3446=over 3447 3448=item * 3449 345064-bit builds 3451 3452Subtest #15 of lib/b.t may fail under 64-bit builds on platforms such 3453as HP-UX PA64 and Linux IA64. The issue is still being investigated. 3454 3455The lib/io_multihomed test may hang in HP-UX if Perl has been 3456configured to be 64-bit. Because other 64-bit platforms do not 3457hang in this test, HP-UX is suspect. All other tests pass 3458in 64-bit HP-UX. The test attempts to create and connect to 3459"multihomed" sockets (sockets which have multiple IP addresses). 3460 3461Note that 64-bit support is still experimental. 3462 3463=item * 3464 3465Failure of Thread tests 3466 3467The subtests 19 and 20 of lib/thr5005.t test are known to fail due to 3468fundamental problems in the 5.005 threading implementation. These are 3469not new failures--Perl 5.005_0x has the same bugs, but didn't have these 3470tests. (Note that support for 5.005-style threading remains experimental.) 3471 3472=item * 3473 3474NEXTSTEP 3.3 POSIX test failure 3475 3476In NEXTSTEP 3.3p2 the implementation of the strftime(3) in the 3477operating system libraries is buggy: the %j format numbers the days of 3478a month starting from zero, which, while being logical to programmers, 3479will cause the subtests 19 to 27 of the lib/posix test may fail. 3480 3481=item * 3482 3483Tru64 (aka Digital UNIX, aka DEC OSF/1) lib/sdbm test failure with gcc 3484 3485If compiled with gcc 2.95 the lib/sdbm test will fail (dump core). 3486The cure is to use the vendor cc, it comes with the operating system 3487and produces good code. 3488 3489=back 3490 3491=head2 EBCDIC platforms not fully supported 3492 3493In earlier releases of Perl, EBCDIC environments like OS390 (also 3494known as Open Edition MVS) and VM-ESA were supported. Due to changes 3495required by the UTF-8 (Unicode) support, the EBCDIC platforms are not 3496supported in Perl 5.6.0. 3497 3498The 5.6.1 release improves support for EBCDIC platforms, but they 3499are not fully supported yet. 3500 3501=head2 UNICOS/mk CC failures during Configure run 3502 3503In UNICOS/mk the following errors may appear during the Configure run: 3504 3505 Guessing which symbols your C compiler and preprocessor define... 3506 CC-20 cc: ERROR File = try.c, Line = 3 3507 ... 3508 bad switch yylook 79bad switch yylook 79bad switch yylook 79bad switch yylook 79#ifdef A29K 3509 ... 3510 4 errors detected in the compilation of "try.c". 3511 3512The culprit is the broken awk of UNICOS/mk. The effect is fortunately 3513rather mild: Perl itself is not adversely affected by the error, only 3514the h2ph utility coming with Perl, and that is rather rarely needed 3515these days. 3516 3517=head2 Arrow operator and arrays 3518 3519When the left argument to the arrow operator C<< -> >> is an array, or 3520the C<scalar> operator operating on an array, the result of the 3521operation must be considered erroneous. For example: 3522 3523 @x->[2] 3524 scalar(@x)->[2] 3525 3526These expressions will get run-time errors in some future release of 3527Perl. 3528 3529=head2 Experimental features 3530 3531As discussed above, many features are still experimental. Interfaces and 3532implementation of these features are subject to change, and in extreme cases, 3533even subject to removal in some future release of Perl. These features 3534include the following: 3535 3536=over 4 3537 3538=item Threads 3539 3540=item Unicode 3541 3542=item 64-bit support 3543 3544=item Lvalue subroutines 3545 3546=item Weak references 3547 3548=item The pseudo-hash data type 3549 3550=item The Compiler suite 3551 3552=item Internal implementation of file globbing 3553 3554=item The DB module 3555 3556=item The regular expression code constructs: 3557 3558C<(?{ code })> and C<(??{ code })> 3559 3560=back 3561 3562=head1 Obsolete Diagnostics 3563 3564=over 4 3565 3566=item Character class syntax [: :] is reserved for future extensions 3567 3568(W) Within regular expression character classes ([]) the syntax beginning 3569with "[:" and ending with ":]" is reserved for future extensions. 3570If you need to represent those character sequences inside a regular 3571expression character class, just quote the square brackets with the 3572backslash: "\[:" and ":\]". 3573 3574=item Ill-formed logical name |%s| in prime_env_iter 3575 3576(W) A warning peculiar to VMS. A logical name was encountered when preparing 3577to iterate over %ENV which violates the syntactic rules governing logical 3578names. Because it cannot be translated normally, it is skipped, and will not 3579appear in %ENV. This may be a benign occurrence, as some software packages 3580might directly modify logical name tables and introduce nonstandard names, 3581or it may indicate that a logical name table has been corrupted. 3582 3583=item In string, @%s now must be written as \@%s 3584 3585The description of this error used to say: 3586 3587 (Someday it will simply assume that an unbackslashed @ 3588 interpolates an array.) 3589 3590That day has come, and this fatal error has been removed. It has been 3591replaced by a non-fatal warning instead. 3592See L</Arrays now always interpolate into double-quoted strings> for 3593details. 3594 3595=item Probable precedence problem on %s 3596 3597(W) The compiler found a bareword where it expected a conditional, 3598which often indicates that an || or && was parsed as part of the 3599last argument of the previous construct, for example: 3600 3601 open FOO || die; 3602 3603=item regexp too big 3604 3605(F) The current implementation of regular expressions uses shorts as 3606address offsets within a string. Unfortunately this means that if 3607the regular expression compiles to longer than 32767, it'll blow up. 3608Usually when you want a regular expression this big, there is a better 3609way to do it with multiple statements. See L<perlre>. 3610 3611=item Use of "$$<digit>" to mean "${$}<digit>" is deprecated 3612 3613(D) Perl versions before 5.004 misinterpreted any type marker followed 3614by "$" and a digit. For example, "$$0" was incorrectly taken to mean 3615"${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004. 3616 3617However, the developers of Perl 5.004 could not fix this bug completely, 3618because at least two widely-used modules depend on the old meaning of 3619"$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the 3620old (broken) way inside strings; but it generates this message as a 3621warning. And in Perl 5.005, this special treatment will cease. 3622 3623=back 3624 3625=head1 Reporting Bugs 3626 3627If you find what you think is a bug, you might check the 3628articles recently posted to the comp.lang.perl.misc newsgroup. 3629There may also be information at http://www.perl.com/ , the Perl 3630Home Page. 3631 3632If you believe you have an unreported bug, please run the B<perlbug> 3633program included with your release. Be sure to trim your bug down 3634to a tiny but sufficient test case. Your bug report, along with the 3635output of C<perl -V>, will be sent off to perlbug@perl.org to be 3636analysed by the Perl porting team. 3637 3638=head1 SEE ALSO 3639 3640The F<Changes> file for exhaustive details on what changed. 3641 3642The F<INSTALL> file for how to build Perl. 3643 3644The F<README> file for general stuff. 3645 3646The F<Artistic> and F<Copying> files for copyright information. 3647 3648=head1 HISTORY 3649 3650Written by Gurusamy Sarathy <F<gsar@ActiveState.com>>, with many 3651contributions from The Perl Porters. 3652 3653Send omissions or corrections to <F<perlbug@perl.org>>. 3654 3655=cut 3656