1package vars; 2 3require 5.002; 4 5# The following require can't be removed during maintenance 6# releases, sadly, because of the risk of buggy code that does 7# require Carp; Carp::croak "..."; without brackets dying 8# if Carp hasn't been loaded in earlier compile time. :-( 9# We'll let those bugs get found on the development track. 10require Carp if $] < 5.00450; 11 12sub import { 13 my $callpack = caller; 14 my ($pack, @imports, $sym, $ch) = @_; 15 foreach $sym (@imports) { 16 if ($sym =~ /::/) { 17 require Carp; 18 Carp::croak("Can't declare another package's variables"); 19 } 20 ($ch, $sym) = unpack('a1a*', $sym); 21 *{"${callpack}::$sym"} = 22 ( $ch eq "\$" ? \$ {"${callpack}::$sym"} 23 : $ch eq "\@" ? \@ {"${callpack}::$sym"} 24 : $ch eq "\%" ? \% {"${callpack}::$sym"} 25 : $ch eq "\*" ? \* {"${callpack}::$sym"} 26 : $ch eq "\&" ? \& {"${callpack}::$sym"} 27 : do { 28 require Carp; 29 Carp::croak("'$ch$sym' is not a valid variable name\n"); 30 }); 31 } 32}; 33 341; 35__END__ 36 37=head1 NAME 38 39vars - Perl pragma to predeclare global variable names 40 41=head1 SYNOPSIS 42 43 use vars qw($frob @mung %seen); 44 45=head1 DESCRIPTION 46 47This will predeclare all the variables whose names are 48in the list, allowing you to use them under "use strict", and 49disabling any typo warnings. 50 51Unlike pragmas that affect the C<$^H> hints variable, the C<use vars> and 52C<use subs> declarations are not BLOCK-scoped. They are thus effective 53for the entire file in which they appear. You may not rescind such 54declarations with C<no vars> or C<no subs>. 55 56Packages such as the B<AutoLoader> and B<SelfLoader> that delay 57loading of subroutines within packages can create problems with 58package lexicals defined using C<my()>. While the B<vars> pragma 59cannot duplicate the effect of package lexicals (total transparency 60outside of the package), it can act as an acceptable substitute by 61pre-declaring global symbols, ensuring their availability to the 62later-loaded routines. 63 64See L<perlmod/Pragmatic Modules>. 65 66=cut 67