1package experimental; 2$experimental::VERSION = '0.020'; 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 $] > 5.011002; 16 } 17 @features; 18}; 19 20my %min_version = ( 21 array_base => '5', 22 autoderef => '5.14.0', 23 bitwise => '5.22.0', 24 const_attr => '5.22.0', 25 current_sub => '5.16.0', 26 declared_refs => '5.26.0', 27 evalbytes => '5.16.0', 28 fc => '5.16.0', 29 lexical_topic => '5.10.0', 30 lexical_subs => '5.18.0', 31 postderef => '5.20.0', 32 postderef_qq => '5.20.0', 33 refaliasing => '5.22.0', 34 regex_sets => '5.18.0', 35 say => '5.10.0', 36 smartmatch => '5.10.0', 37 signatures => '5.20.0', 38 state => '5.10.0', 39 switch => '5.10.0', 40 unicode_eval => '5.16.0', 41 unicode_strings => '5.12.0', 42); 43my %max_version = ( 44 autoderef => '5.23.1', 45 lexical_topic => '5.23.4', 46); 47 48$_ = version->new($_) for values %min_version; 49$_ = version->new($_) for values %max_version; 50 51my %additional = ( 52 postderef => ['postderef_qq'], 53 switch => ['smartmatch'], 54 declared_refs => ['refaliasing'], 55); 56 57sub _enable { 58 my $pragma = shift; 59 if ($warnings{"experimental::$pragma"}) { 60 warnings->unimport("experimental::$pragma"); 61 feature->import($pragma) if exists $features{$pragma}; 62 _enable(@{ $additional{$pragma} }) if $additional{$pragma}; 63 } 64 elsif ($features{$pragma}) { 65 feature->import($pragma); 66 _enable(@{ $additional{$pragma} }) if $additional{$pragma}; 67 } 68 elsif (not exists $min_version{$pragma}) { 69 croak "Can't enable unknown feature $pragma"; 70 } 71 elsif ($] < $min_version{$pragma}) { 72 my $stable = $min_version{$pragma}; 73 if ($stable->{version}[1] % 2) { 74 $stable = version->new( 75 "5.".($stable->{version}[1]+1).'.0' 76 ); 77 } 78 croak "Need perl $stable or later for feature $pragma"; 79 } 80 elsif ($] >= ($max_version{$pragma} || 7)) { 81 croak "Experimental feature $pragma has been removed from perl in version $max_version{$pragma}"; 82 } 83} 84 85sub import { 86 my ($self, @pragmas) = @_; 87 88 for my $pragma (@pragmas) { 89 _enable($pragma); 90 } 91 return; 92} 93 94sub _disable { 95 my $pragma = shift; 96 if ($warnings{"experimental::$pragma"}) { 97 warnings->import("experimental::$pragma"); 98 feature->unimport($pragma) if exists $features{$pragma}; 99 _disable(@{ $additional{$pragma} }) if $additional{$pragma}; 100 } 101 elsif ($features{$pragma}) { 102 feature->unimport($pragma); 103 _disable(@{ $additional{$pragma} }) if $additional{$pragma}; 104 } 105 elsif (not exists $min_version{$pragma}) { 106 carp "Can't disable unknown feature $pragma, ignoring"; 107 } 108} 109 110sub unimport { 111 my ($self, @pragmas) = @_; 112 113 for my $pragma (@pragmas) { 114 _disable($pragma); 115 } 116 return; 117} 118 1191; 120 121#ABSTRACT: Experimental features made easy 122 123__END__ 124 125=pod 126 127=encoding UTF-8 128 129=head1 NAME 130 131experimental - Experimental features made easy 132 133=head1 VERSION 134 135version 0.020 136 137=head1 SYNOPSIS 138 139 use experimental 'lexical_subs', 'smartmatch'; 140 my sub foo { $_[0] ~~ 1 } 141 142=head1 DESCRIPTION 143 144This pragma provides an easy and convenient way to enable or disable 145experimental features. 146 147Every version of perl has some number of features present but considered 148"experimental." For much of the life of Perl 5, this was only a designation 149found in the documentation. Starting in Perl v5.10.0, and more aggressively in 150v5.18.0, experimental features were placed behind pragmata used to enable the 151feature and disable associated warnings. 152 153The C<experimental> pragma exists to combine the required incantations into a 154single interface stable across releases of perl. For every experimental 155feature, this should enable the feature and silence warnings for the enclosing 156lexical scope: 157 158 use experimental 'feature-name'; 159 160To disable the feature and, if applicable, re-enable any warnings, use: 161 162 no experimental 'feature-name'; 163 164The supported features, documented further below, are: 165 166=over 4 167 168=item * C<array_base> - allow the use of C<$[> to change the starting index of C<@array>. 169 170This is supported on all versions of perl. 171 172=item * C<autoderef> - allow push, each, keys, and other built-ins on references. 173 174This was added in perl 5.14.0 and removed in perl 5.23.1. 175 176=item * C<bitwise> - allow the new stringwise bit operators 177 178This was added in perl 5.22.0. 179 180=item * C<const_attr> - allow the :const attribute on subs 181 182This was added in perl 5.22.0. 183 184=item * C<lexical_topic> - allow the use of lexical C<$_> via C<my $_>. 185 186This was added in perl 5.10.0 and removed in perl 5.23.4. 187 188=item * C<lexical_subs> - allow the use of lexical subroutines. 189 190This was added in 5.18.0. 191 192=item * C<postderef> - allow the use of postfix dereferencing expressions, 193including in interpolating strings 194 195This was added in perl 5.20.0. 196 197=item * C<re_strict> - enables strict mode in regular expressions 198 199This was added in perl 5.22.0. 200 201=item * C<refaliasing> - allow aliasing via C<\$x = \$y> 202 203This was added in perl 5.22.0. 204 205=item * C<regex_sets> - allow extended bracketed character classes in regexps 206 207This was added in perl 5.18.0. 208 209=item * C<signatures> - allow subroutine signatures (for named arguments) 210 211This was added in perl 5.20.0. 212 213=item * C<smartmatch> - allow the use of C<~~> 214 215This was added in perl 5.10.0, but it should be noted there are significant 216incompatibilities between 5.10.0 and 5.10.1. 217 218=item * C<switch> - allow the use of C<~~>, given, and when 219 220This was added in perl 5.10.0. 221 222=item * C<win32_perlio> - allows the use of the :win32 IO layer. 223 224This was added on perl 5.22.0. 225 226=back 227 228=head2 Ordering matters 229 230Using this pragma to 'enable an experimental feature' is another way of saying 231that this pragma will disable the warnings which would result from using that 232feature. Therefore, the order in which pragmas are applied is important. In 233particular, you probably want to enable experimental features I<after> you 234enable warnings: 235 236 use warnings; 237 use experimental 'smartmatch'; 238 239You also need to take care with modules that enable warnings for you. A common 240example being Moose. In this example, warnings for the 'smartmatch' feature are 241first turned on by the warnings pragma, off by the experimental pragma and back 242on again by the Moose module (fix is to switch the last two lines): 243 244 use warnings; 245 use experimental 'smartmatch'; 246 use Moose; 247 248=head2 Disclaimer 249 250Because of the nature of the features it enables, forward compatibility can not 251be guaranteed in any way. 252 253=head1 SEE ALSO 254 255L<perlexperimental|perlexperimental> contains more information about experimental features. 256 257=head1 AUTHOR 258 259Leon Timmermans <leont@cpan.org> 260 261=head1 COPYRIGHT AND LICENSE 262 263This software is copyright (c) 2013 by Leon Timmermans. 264 265This is free software; you can redistribute it and/or modify it under 266the same terms as the Perl 5 programming language system itself. 267 268=cut 269