--- name: "perlexperiment" section: "1" platform: "linux" package: "perl-doc" version: "5.40.1-6+deb13u1" release: "Debian 13 (Trixie)" platforms: ["linux", "openbsd"] url: "https://new.carta.tech/perlexperiment" --- # perlexperiment(1) A listing of experimental features in Perl ## 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 Deprecated in 5.38.0 Will be removed in 5.42.0 Using this feature triggers warnings in the category `"deprecated"`. The ticket for this experiment is \[perl #13173\] \. - Pluggable keywords Introduced in Perl 5.11.2 See "PL\_keyword\_plugin" in perlapi for the mechanism. The ticket for this experiment is \[perl #13199\] \. - Aliasing via reference Introduced in Perl 5.22.0 Using this feature triggers warnings in the category `"experimental::refaliasing"`. The ticket for this experiment is \[perl #14150\] \. See also: "Assigning to References" in perlref - 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 \[perl #18755\] \ See "'strict' mode" in re - 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 \[perl #15458\] \. See also: "Declaring a Reference to a Variable" in perlref - There is an "installhtml" target in the Makefile. The ticket for this experiment is \[perl #12726\] \. - (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 \[perl #18756\] \. See also: "(\*positive\_lookbehind:*pattern*)" in perlre and "(\*negative\_lookbehind:*pattern*)" in perlre - 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 `"experimental::private_use"`. The ticket for this experiment is \[perl #18758\] \. - 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 \[perl #18759\] \. - try/catch control structure Introduced in Perl 5.34.0. Using the optional `"finally"` block part of this feature triggers warnings in the category `"experimental::try"`. The ticket for this experiment is \[perl #18760\] \ - Use of @\_ 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 (`@_`) within a subroutine that uses signatures will emit a warning in the category `"experimental::args_array_with_signatures"`. This includes `@_` directly, elements of it such as `$_[$index]`, or situations where the default arguments array is accessed implicitly such as `"shift"` or `"pop"` without arguments. - The builtin namespace Introduced in Perl 5.36.0. Using certain functions of this feature triggers warnings in the category `"experimental::builtin"`. In Perl 5.36.0, a new namespace, `"builtin"`, 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 \[perl #19764\] \. - The defer block modifier Introduced in Perl 5.36.0 Using this feature triggers warnings in the category `"experimental::defer"`. This feature adds a new kind of block, a `"defer"` block, which will not be executed until the containing block is being exited. The ticket for this experiment is \[perl #17949\] \. - Extra paired delimiters for quote-like operators Introduced in Perl 5.36.0 Using this feature triggers warnings in the category `"experimental::extra_paired_delimiters"`. 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 \[perl #19765\] \. ### 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 - Internal file glob Introduced in Perl 5.6.0 - **fork()** emulation Introduced in Perl 5.6.1 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 - Postfix dereference syntax Introduced in Perl 5.20.0 Accepted in Perl 5.24.0 - Lexical subroutines Introduced in Perl 5.18.0 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 - The infix "isa" operator Introduced in Perl 5.32.0 Accepted in Perl 5.36.0 - Subroutine signatures Introduced in Perl 5.20.0 Accepted in Perl 5.36.0 - Regular Expression Set Operations Introduced in Perl 5.18 Accepted in Perl 5.36 See : "Extended Bracketed Character Classes" in perlrecharclass - try/catch control structure Introduced in Perl 5.34.0. Accepted in Perl 5.40 when not using the optional `"finally"` block. - The "const" attribute Introduced in Perl 5.22.0 Accepted in Perl 5.40 See also: "Constant Functions" in perlsub - for loop with multiple iteration variables Introduced in Perl 5.36.0. Accepted in Perl 5.40. This feature enables a parenthesized list of iteration variables for `"for"` rather than a single variable. ### 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 Removed in Perl 5.11.3 - Lexical $\_ Using this feature triggered warnings in the category `"experimental::lexical_topic"`. 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 - The ":win32" IO pseudolayer Introduced in Perl 5.8.0 (or before) Removed in Perl 5.36.0 ## SEE ALSO For a complete list of features check feature. ## AUTHORS brian d foy `""` Sébastien Aperghis-Tramoni `""` ## COPYRIGHT Copyright 2010, brian d foy `""` ## LICENSE You can use and redistribute this document under the same terms as Perl itself.