=encoding utf-8 =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 Deprecated in 5.38.0 Will be removed in 5.42.0 Using this feature triggers warnings in the category C. The ticket for this experiment is L<[perl #13173]|https://github.com/Perl/perl5/issues/13173>. =item Pluggable keywords Introduced in Perl 5.11.2 See L for the mechanism. The ticket for this experiment is L<[perl #13199]|https://github.com/Perl/perl5/issues/13199>. =item Aliasing via reference Introduced in Perl 5.22.0 Using this feature triggers warnings in the category C. The ticket for this experiment is L<[perl #14150]|https://github.com/Perl/perl5/issues/14150>. See also: L =item The "const" attribute Introduced in Perl 5.22.0 Using this feature triggers warnings in the category C. The ticket for this experiment is L<[perl #14428]|https://github.com/Perl/perl5/issues/14428>. See also: L =item use re 'strict'; Introduced in Perl 5.22.0 Using this feature triggers warnings in the category C. The ticket for this experiment is L<[perl #18755]|https://github.com/Perl/perl5/issues/18755> See L =item Declaring a reference to a variable Introduced in Perl 5.26.0 Using this feature triggers warnings in the category C. The ticket for this experiment is L<[perl #15458]|https://github.com/Perl/perl5/issues/15458>. See also: L =item There is an C target in the Makefile. The ticket for this experiment 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. The ticket for this experiment is L<[perl #18756]|https://github.com/Perl/perl5/issues/18756>. See also: L)> and L)> =item Unicode private use character hooks Introduced in Perl 5.30.0. This feature is part of an interface intended for internal and experimental use by the perl5 developers. You are unlikely to encounter it in the wild. Using this feature triggers warnings in the category C. The ticket for this experiment is L<[perl #18758]|https://github.com/Perl/perl5/issues/18758>. =item 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 C. The ticket for this experiment is L<[perl #18759]|https://github.com/Perl/perl5/issues/18759>. =item try/catch control structure Introduced in Perl 5.34.0. Using this feature triggers warnings in the category C. The ticket for this experiment is L<[perl #18760]|https://github.com/Perl/perl5/issues/18760> =item Use of C<@_> within subroutine signatures Introduced in Perl 5.36.0 as part of a reduction in the scope of experimental subroutine signatures. Using the default arguments array (C<@_>) within a subroutine that uses signatures will emit a warning in the category C. This includes C<@_> directly, elements of it such as C<$_[$index]>, or situations where the default arguments array is accessed implicitly such as C or C without arguments. =item for loop with multiple iteration variables Introduced in Perl 5.36.0. Using this feature triggers warnings in the category C. This feature enables a parenthesized list of iteration variables for C rather than a single variable. The ticket for this experiment is L<[perl #18744]|https://github.com/Perl/perl5/issues/18744>. =item The builtin namespace Introduced in Perl 5.36.0. Using this feature triggers warnings in the category C. In Perl 5.36.0, a new namespace, C, was created for new core functions that will not be present in every namespace, but will be available for importing. The namespace itself was considered experimental until Perl 5.39.2. Some specific functions within it remain experimental. The ticket for this experiment is L<[perl #19764]|https://github.com/Perl/perl5/issues/19764>. =item The defer block modifier Introduced in Perl 5.36.0 Using this feature triggers warnings in the category C. This feature adds a new kind of block, a C block, which will not be executed until the containing block is being exited. The ticket for this experiment is L<[perl #17949]|https://github.com/Perl/perl5/issues/17949>. =item Extra paired delimiters for quote-like operators Introduced in Perl 5.36.0 Using this feature triggers warnings in the category C. This feature allows for many non-ASCII pairs of mirroring delimiters, for example: my @array = qw« tinker tailor soldier spy »; The ticket for this experiment is L<[perl #19765]|https://github.com/Perl/perl5/issues/19765>. =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, L =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 =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 =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 =item Lvalue subroutines Introduced in Perl 5.6.0 Accepted in Perl 5.20.0 See also L =item Backtracking control verbs C<(*ACCEPT)> Introduced in Perl 5.10 Accepted in Perl 5.20.0 =item The C<:pop> IO pseudolayer See also L 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 =item The infix C operator Introduced in Perl 5.32.0 Accepted in Perl 5.36.0 =item Subroutine signatures Introduced in Perl 5.20.0 Accepted in Perl 5.36.0 =item Regular Expression Set Operations Introduced in Perl 5.18 Accepted in Perl 5.36 See : L =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). =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 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 The experimental C pragma was swallowed by the C 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. 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. Superseded by L. Introduced in Perl 5.14.0 Removed in Perl 5.24.0 =item C can have an experimental optional attribute C Introduced in Perl 5.8.0 Deprecated in Perl 5.10.0 Removed in Perl 5.28.0 =item The C<:win32> IO pseudolayer Introduced in Perl 5.8.0 (or before) Removed in Perl 5.36.0 =back =head1 SEE ALSO For a complete list of features check L. =head1 AUTHORS brian d foy C<< >> SEbastien Aperghis-Tramoni C<< >> =head1 COPYRIGHT Copyright 2010, brian d foy C<< >> =head1 LICENSE You can use and redistribute this document under the same terms as Perl itself. =cut