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PERLEXPERIMENT(1) Perl Programmers Reference Guide PERLEXPERIMENT(1) NAME perlexperiment - A listing of experimental features in Perl 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. Current experiments Smart match ("~~") Introduced in Perl 5.10.0 Modified in Perl 5.10.1, 5.12.0 Using this feature triggers warnings in the category "experimental::smartmatch". The ticket for this experiment is [perl #13173] <https://github.com/Perl/perl5/issues/13173>. Pluggable keywords Introduced in Perl 5.11.2 See "PL_keyword_plugin" in perlapi for the mechanism. The ticket for this experiment is [perl #13199] <https://github.com/Perl/perl5/issues/13199>. Regular Expression Set Operations Introduced in Perl 5.18 Using this feature triggers warnings in the category "experimental::regex_sets". The ticket for this experiment is [perl #13197] <https://github.com/Perl/perl5/issues/13197>. See also: "Extended Bracketed Character Classes" in perlrecharclass Subroutine signatures Introduced in Perl 5.20.0 Using this feature triggers warnings in the category "experimental::signatures". The ticket for this experiment is [perl #13681] <https://github.com/Perl/perl5/issues/13681>. Aliasing via reference Introduced in Perl 5.22.0 See also: "Assigning to References" in perlref The "const" attribute Introduced in Perl 5.22.0 Using this feature triggers warnings in the category "experimental::const_attr". The ticket for this experiment is [perl #14428] <https://github.com/Perl/perl5/issues/14428>. See also: "Constant Functions" in perlsub use re 'strict'; Introduced in Perl 5.22.0 Using this feature triggers warnings in the category "experimental::re_strict". The ticket for this experiment is [perl #18755] <https://github.com/Perl/perl5/issues/18755> See "'strict' mode" in re The <:win32> IO pseudolayer Using this feature triggers warnings in the category "experimental::win32_perlio". The ticket for this experiment is [perl #13198] <https://github.com/Perl/perl5/issues/13198>. See also "PERLIO" in perlrun Declaring a reference to a variable Introduced in Perl 5.26.0 Using this feature triggers warnings in the category "experimental::declared_refs". The ticket for this experiment is [perl #15458] <https://github.com/Perl/perl5/issues/15458>. See also: "Declaring a Reference to a Variable" in perlref There is an "installhtml" target in the Makefile. The ticket for this experiment is [perl #12726] <https://github.com/Perl/perl5/issues/12726>. (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 "experimental::vlb". The ticket for this experiment is [perl #18756] <https://github.com/Perl/perl5/issues/18756>. experimental use by the perl5 developers. You are unlikely to encounter it in the wild. Using this feature triggers warnings in the category "experimental::private_use". The ticket for this experiment is [perl #18758] <https://github.com/Perl/perl5/issues/18758>. Unicode property wildcards Introduced in Perl 5.30.0. This feature allows regular expression matching against Unicode character properties to be expressed more concisely. Using this feature triggers warnings in the category "experimental::uniprop_wildcards". The ticket for this experiment is [perl #18759] <https://github.com/Perl/perl5/issues/18759>. isa infix operator Introduced in Perl 5.32.0. Using this feature triggers warnings in the category "experimental::isa". The ticket for this experiment is [perl #18754] <https://github.com/Perl/perl5/issues/18754> try/catch control structure Introduced in Perl 5.34.0. Using this feature triggers warnings in the category "experimental::try". The ticket for this experiment is [perl #18760] <https://github.com/Perl/perl5/issues/18760> 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. 64-bit support Introduced in Perl 5.005 die accepts a reference Introduced in Perl 5.005 DB module Introduced in Perl 5.6.0 See also perldebug, perldebtut Weak references Introduced in Perl 5.6.0 See also perlfork -Dusemultiplicity -Duseithreads Introduced in Perl 5.6.0 Accepted in Perl 5.8.0 Support for long doubles Introduced in Perl 5.6.0 Accepted in Perl 5.8.1 The "\N" regex character class The "\N" character class, not to be confused with the named character sequence "\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. "(?{code})" and "(??{ code })" Introduced in Perl 5.6.0 Accepted in Perl 5.20.0 See also perlre 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 Socket Lvalue subroutines Introduced in Perl 5.6.0 Accepted in Perl 5.20.0 See also perlsub Backtracking control verbs "(*ACCEPT)" Introduced in Perl 5.10 Accepted in Perl 5.20.0 The <:pop> IO pseudolayer See also "PERLIO" in perlrun Accepted in Perl 5.20.0 "\s" in regexp matches vertical tab Accepted in Perl 5.22.0 Accepted in Perl 5.26.0 String- and number-specific bitwise operators Introduced in Perl 5.22.0 Accepted in Perl 5.28.0 Alphabetic assertions Introduced in Perl 5.28.0 Accepted in Perl 5.32.0 Script runs Introduced in Perl 5.28.0 Accepted in Perl 5.32.0 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 perlpolicy). 5.005-style threading Introduced in Perl 5.005 Removed in Perl 5.10 perlcc Introduced in Perl 5.005 Moved from Perl 5.9.0 to CPAN The pseudo-hash data type Introduced in Perl 5.6.0 Removed in Perl 5.9.0 GetOpt::Long Options can now take multiple values at once (experimental) "Getopt::Long" upgraded to version 2.35 Removed in Perl 5.8.8 Assertions The "-A" command line switch Introduced in Perl 5.9.0 Removed in Perl 5.9.5 Test::Harness::Straps Moved from Perl 5.10.1 to CPAN "legacy" The experimental "legacy" pragma was swallowed by the "feature" pragma. Introduced in Perl 5.11.2 Introduced in Perl 5.10.0 Removed in Perl 5.24.0 Array and hash container functions accept references Using this feature triggered warnings in the category "experimental::autoderef". Superseded by "Postfix dereference syntax". Introduced in Perl 5.14.0 Removed in Perl 5.24.0 "our" can have an experimental optional attribute "unique" Introduced in Perl 5.8.0 Deprecated in Perl 5.10.0 Removed in Perl 5.28.0 SEE ALSO For a complete list of features check feature. AUTHORS brian d foy "<brian.d.foy@gmail.com>" Sebastien Aperghis-Tramoni "<saper@cpan.org>" COPYRIGHT Copyright 2010, brian d foy "<brian.d.foy@gmail.com>" LICENSE You can use and redistribute this document under the same terms as Perl itself. perl v5.34.3 2023-11-28 PERLEXPERIMENT(1)