=head1 NAME perlexperiment - A listing of experimental features in Perl =head1 DESCRIPTION This document lists the current and past experimental features in the perl core. Although all of these are documented with their appropriate topics, this succinct listing gives you an overview and basic facts about their status. So far we've merely tried to find and list the experimental features and infer their inception, versions, etc. There's a lot of speculation here. =head2 Current experiments =over 8 =item Smart match (C<~~>) Introduced in Perl 5.10.0 Modified in Perl 5.10.1, 5.12.0 Using this feature triggers warnings in the category C<experimental::smartmatch>. The ticket for this feature is L<[perl #13173]|https://github.com/Perl/perl5/issues/13173>. =item Pluggable keywords The ticket for this feature is L<[perl #13199]|https://github.com/Perl/perl5/issues/13199>. See L<perlapi/PL_keyword_plugin> for the mechanism. Introduced in Perl 5.11.2 =item Regular Expression Set Operations Introduced in Perl 5.18 The ticket for this feature is L<[perl #13197]|https://github.com/Perl/perl5/issues/13197>. See also: L<perlrecharclass/Extended Bracketed Character Classes> Using this feature triggers warnings in the category C<experimental::regex_sets>. =item Subroutine signatures Introduced in Perl 5.20.0 Using this feature triggers warnings in the category C<experimental::signatures>. The ticket for this feature is L<[perl #13681]|https://github.com/Perl/perl5/issues/13681>. =item Aliasing via reference Introduced in Perl 5.22.0 Using this feature triggers warnings in the category C<experimental::refaliasing>. The ticket for this feature is L<[perl #14150]|https://github.com/Perl/perl5/issues/14150>. See also: L<perlref/Assigning to References> =item The "const" attribute Introduced in Perl 5.22.0 Using this feature triggers warnings in the category C<experimental::const_attr>. The ticket for this feature is L<[perl #14428]|https://github.com/Perl/perl5/issues/14428>. See also: L<perlsub/Constant Functions> =item use re 'strict'; Introduced in Perl 5.22.0 Using this feature triggers warnings in the category C<experimental::re_strict>. See L<re/'strict' mode> =item The <:win32> IO pseudolayer The ticket for this feature is L<[perl #13198]|https://github.com/Perl/perl5/issues/13198>. See also L<perlrun/PERLIO> =item Declaring a reference to a variable Introduced in Perl 5.26.0 Using this feature triggers warnings in the category C<experimental::declared_refs>. The ticket for this feature is L<[perl #15458]|https://github.com/Perl/perl5/issues/15458>. See also: L<perlref/Declaring a Reference to a Variable> =item There is an C<installhtml> target in the Makefile. The ticket for this feature is L<[perl #12726]|https://github.com/Perl/perl5/issues/12726>. =item (Limited) Variable-length look-behind Introduced in Perl 5.30.0. Variability of up to 255 characters is handled. Using this feature triggers warnings in the category C<experimental::vlb>. See also: L<perlre/(*positive_lookbehind:I<pattern>)> and L<perlre/(*negative_lookbehind:I<pattern>)> =back =head2 Accepted features These features were so wildly successful and played so well with others that we decided to remove their experimental status and admit them as full, stable features in the world of Perl, lavishing all the benefits and luxuries thereof. They are also awarded +5 Stability and +3 Charisma. =over 8 =item 64-bit support Introduced in Perl 5.005 =item die accepts a reference Introduced in Perl 5.005 =item DB module Introduced in Perl 5.6.0 See also L<perldebug>, L<perldebtut> =item Weak references Introduced in Perl 5.6.0 =item Internal file glob Introduced in Perl 5.6.0 =item fork() emulation Introduced in Perl 5.6.1 See also L<perlfork> =item -Dusemultiplicity -Duseithreads Introduced in Perl 5.6.0 Accepted in Perl 5.8.0 =item Support for long doubles Introduced in Perl 5.6.0 Accepted in Perl 5.8.1 =item The C<\N> regex character class The C<\N> character class, not to be confused with the named character sequence C<\N{NAME}>, denotes any non-newline character in a regular expression. Introduced in Perl 5.12 Exact version of acceptance unclear, but no later than Perl 5.18. =item C<(?{code})> and C<(??{ code })> Introduced in Perl 5.6.0 Accepted in Perl 5.20.0 See also L<perlre> =item Linux abstract Unix domain sockets Introduced in Perl 5.9.2 Accepted before Perl 5.20.0. The Socket library is now primarily maintained on CPAN, rather than in the perl core. See also L<Socket> =item Lvalue subroutines Introduced in Perl 5.6.0 Accepted in Perl 5.20.0 See also L<perlsub> =item Backtracking control verbs C<(*ACCEPT)> Introduced in Perl 5.10 Accepted in Perl 5.20.0 =item The <:pop> IO pseudolayer See also L<perlrun/PERLIO> Accepted in Perl 5.20.0 =item C<\s> in regexp matches vertical tab Accepted in Perl 5.22.0 =item Postfix dereference syntax Introduced in Perl 5.20.0 Accepted in Perl 5.24.0 =item Lexical subroutines Introduced in Perl 5.18.0 Accepted in Perl 5.26.0 =item String- and number-specific bitwise operators Introduced in Perl 5.22.0 Accepted in Perl 5.28.0 =item Alphabetic assertions Introduced in Perl 5.28.0 Accepted in Perl 5.32.0 =item Script runs Introduced in Perl 5.28.0 Accepted in Perl 5.32.0 =back =head2 Removed features These features are no longer considered experimental and their functionality has disappeared. It's your own fault if you wrote production programs using these features after we explicitly told you not to (see L<perlpolicy>). =over 8 =item 5.005-style threading Introduced in Perl 5.005 Removed in Perl 5.10 =item perlcc Introduced in Perl 5.005 Moved from Perl 5.9.0 to CPAN =item The pseudo-hash data type Introduced in Perl 5.6.0 Removed in Perl 5.9.0 =item GetOpt::Long Options can now take multiple values at once (experimental) C<Getopt::Long> upgraded to version 2.35 Removed in Perl 5.8.8 =item Assertions The C<-A> command line switch Introduced in Perl 5.9.0 Removed in Perl 5.9.5 =item Test::Harness::Straps Moved from Perl 5.10.1 to CPAN =item C<legacy> The experimental C<legacy> pragma was swallowed by the C<feature> pragma. Introduced in Perl 5.11.2 Removed in Perl 5.11.3 =item Lexical C<$_> Using this feature triggered warnings in the category C<experimental::lexical_topic>. Introduced in Perl 5.10.0 Removed in Perl 5.24.0 =item Array and hash container functions accept references Using this feature triggered warnings in the category C<experimental::autoderef>. Superseded by L</Postfix dereference syntax>. Introduced in Perl 5.14.0 Removed in Perl 5.24.0 =item C<our> can have an experimental optional attribute C<unique> Introduced in Perl 5.8.0 Deprecated in Perl 5.10.0 Removed in Perl 5.28.0 =back =head1 SEE ALSO For a complete list of features check L<feature>. =head1 AUTHORS brian d foy C<< <brian.d.foy@gmail.com> >> SE<eacute>bastien Aperghis-Tramoni C<< <saper@cpan.org> >> =head1 COPYRIGHT Copyright 2010, brian d foy C<< <brian.d.foy@gmail.com> >> =head1 LICENSE You can use and redistribute this document under the same terms as Perl itself. =cut