1package experimental; 2$experimental::VERSION = '0.019'; 3use strict; 4use warnings; 5use version (); 6 7BEGIN { eval { require feature } }; 8use Carp qw/croak carp/; 9 10my %warnings = map { $_ => 1 } grep { /^experimental::/ } keys %warnings::Offsets; 11my %features = map { $_ => 1 } $] > 5.015006 ? keys %feature::feature : do { 12 my @features; 13 if ($] >= 5.010) { 14 push @features, qw/switch say state/; 15 push @features, 'unicode_strings' if $] > 5.011002; 16 } 17 @features; 18}; 19 20my %min_version = ( 21 array_base => '5', 22 autoderef => '5.14.0', 23 bitwise => '5.22.0', 24 const_attr => '5.22.0', 25 current_sub => '5.16.0', 26 evalbytes => '5.16.0', 27 fc => '5.16.0', 28 lexical_topic => '5.10.0', 29 lexical_subs => '5.18.0', 30 postderef => '5.20.0', 31 postderef_qq => '5.20.0', 32 refaliasing => '5.22.0', 33 regex_sets => '5.18.0', 34 say => '5.10.0', 35 smartmatch => '5.10.0', 36 signatures => '5.20.0', 37 state => '5.10.0', 38 switch => '5.10.0', 39 unicode_eval => '5.16.0', 40 unicode_strings => '5.12.0', 41); 42my %max_version = ( 43 autoderef => '5.23.1', 44 lexical_topic => '5.23.4', 45); 46 47$_ = version->new($_) for values %min_version; 48$_ = version->new($_) for values %max_version; 49 50my %additional = ( 51 postderef => ['postderef_qq'], 52 switch => ['smartmatch'], 53); 54 55sub _enable { 56 my $pragma = shift; 57 if ($warnings{"experimental::$pragma"}) { 58 warnings->unimport("experimental::$pragma"); 59 feature->import($pragma) if exists $features{$pragma}; 60 _enable(@{ $additional{$pragma} }) if $additional{$pragma}; 61 } 62 elsif ($features{$pragma}) { 63 feature->import($pragma); 64 _enable(@{ $additional{$pragma} }) if $additional{$pragma}; 65 } 66 elsif (not exists $min_version{$pragma}) { 67 croak "Can't enable unknown feature $pragma"; 68 } 69 elsif ($] < $min_version{$pragma}) { 70 my $stable = $min_version{$pragma}; 71 if ($stable->{version}[1] % 2) { 72 $stable = version->new( 73 "5.".($stable->{version}[1]+1).'.0' 74 ); 75 } 76 croak "Need perl $stable or later for feature $pragma"; 77 } 78 elsif ($] >= ($max_version{$pragma} || 7)) { 79 croak "Experimental feature $pragma has been removed from perl in version $max_version{$pragma}"; 80 } 81} 82 83sub import { 84 my ($self, @pragmas) = @_; 85 86 for my $pragma (@pragmas) { 87 _enable($pragma); 88 } 89 return; 90} 91 92sub _disable { 93 my $pragma = shift; 94 if ($warnings{"experimental::$pragma"}) { 95 warnings->import("experimental::$pragma"); 96 feature->unimport($pragma) if exists $features{$pragma}; 97 _disable(@{ $additional{$pragma} }) if $additional{$pragma}; 98 } 99 elsif ($features{$pragma}) { 100 feature->unimport($pragma); 101 _disable(@{ $additional{$pragma} }) if $additional{$pragma}; 102 } 103 elsif (not exists $min_version{$pragma}) { 104 carp "Can't disable unknown feature $pragma, ignoring"; 105 } 106} 107 108sub unimport { 109 my ($self, @pragmas) = @_; 110 111 for my $pragma (@pragmas) { 112 _disable($pragma); 113 } 114 return; 115} 116 1171; 118 119#ABSTRACT: Experimental features made easy 120 121__END__ 122 123=pod 124 125=encoding UTF-8 126 127=head1 NAME 128 129experimental - Experimental features made easy 130 131=head1 VERSION 132 133version 0.019 134 135=head1 SYNOPSIS 136 137 use experimental 'lexical_subs', 'smartmatch'; 138 my sub foo { $_[0] ~~ 1 } 139 140=head1 DESCRIPTION 141 142This pragma provides an easy and convenient way to enable or disable 143experimental features. 144 145Every version of perl has some number of features present but considered 146"experimental." For much of the life of Perl 5, this was only a designation 147found in the documentation. Starting in Perl v5.10.0, and more aggressively in 148v5.18.0, experimental features were placed behind pragmata used to enable the 149feature and disable associated warnings. 150 151The C<experimental> pragma exists to combine the required incantations into a 152single interface stable across releases of perl. For every experimental 153feature, this should enable the feature and silence warnings for the enclosing 154lexical scope: 155 156 use experimental 'feature-name'; 157 158To disable the feature and, if applicable, re-enable any warnings, use: 159 160 no experimental 'feature-name'; 161 162The supported features, documented further below, are: 163 164=over 4 165 166=item * C<array_base> - allow the use of C<$[> to change the starting index of C<@array>. 167 168This is supported on all versions of perl. 169 170=item * C<autoderef> - allow push, each, keys, and other built-ins on references. 171 172This was added in perl 5.14.0 and removed in perl 5.23.1. 173 174=item * C<bitwise> - allow the new stringwise bit operators 175 176This was added in perl 5.22.0. 177 178=item * C<const_attr> - allow the :const attribute on subs 179 180This was added in perl 5.22.0. 181 182=item * C<lexical_topic> - allow the use of lexical C<$_> via C<my $_>. 183 184This was added in perl 5.10.0 and removed in perl 5.23.4. 185 186=item * C<lexical_subs> - allow the use of lexical subroutines. 187 188This was added in 5.18.0. 189 190=item * C<postderef> - allow the use of postfix dereferencing expressions, 191including in interpolating strings 192 193This was added in perl 5.20.0. 194 195=item * C<re_strict> - enables strict mode in regular expressions 196 197This was added in perl 5.22.0. 198 199=item * C<refaliasing> - allow aliasing via C<\$x = \$y> 200 201This was added in perl 5.22.0. 202 203=item * C<regex_sets> - allow extended bracketed character classes in regexps 204 205This was added in perl 5.18.0. 206 207=item * C<signatures> - allow subroutine signatures (for named arguments) 208 209This was added in perl 5.20.0. 210 211=item * C<smartmatch> - allow the use of C<~~> 212 213This was added in perl 5.10.0, but it should be noted there are significant 214incompatibilities between 5.10.0 and 5.10.1. 215 216=item * C<switch> - allow the use of C<~~>, given, and when 217 218This was added in perl 5.10.0. 219 220=item * C<win32_perlio> - allows the use of the :win32 IO layer. 221 222This was added on perl 5.22.0. 223 224=back 225 226=head2 Ordering matters 227 228Using this pragma to 'enable an experimental feature' is another way of saying 229that this pragma will disable the warnings which would result from using that 230feature. Therefore, the order in which pragmas are applied is important. In 231particular, you probably want to enable experimental features I<after> you 232enable warnings: 233 234 use warnings; 235 use experimental 'smartmatch'; 236 237You also need to take care with modules that enable warnings for you. A common 238example being Moose. In this example, warnings for the 'smartmatch' feature are 239first turned on by the warnings pragma, off by the experimental pragma and back 240on again by the Moose module (fix is to switch the last two lines): 241 242 use warnings; 243 use experimental 'smartmatch'; 244 use Moose; 245 246=head2 Disclaimer 247 248Because of the nature of the features it enables, forward compatibility can not 249be guaranteed in any way. 250 251=head1 SEE ALSO 252 253L<perlexperimental|perlexperimental> contains more information about experimental features. 254 255=head1 AUTHOR 256 257Leon Timmermans <leont@cpan.org> 258 259=head1 COPYRIGHT AND LICENSE 260 261This software is copyright (c) 2013 by Leon Timmermans. 262 263This is free software; you can redistribute it and/or modify it under 264the same terms as the Perl 5 programming language system itself. 265 266=cut 267