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 feature is [perl #13173] <https://github.com/Perl/perl5/issues/13173>.

Pluggable keywords
    The ticket for this feature is [perl #13199] <https://github.com/Perl/perl5/issues/13199>.

    See "PL_keyword_plugin" in perlapi for the mechanism.

    Introduced in Perl 5.11.2

Regular Expression Set Operations
    Introduced in Perl 5.18

    The ticket for this feature is [perl #13197] <https://github.com/Perl/perl5/issues/13197>.

    See also: "Extended Bracketed Character Classes" in perlrecharclass

    Using this feature triggers warnings in the category "experimental::regex_sets".

Subroutine signatures
    Introduced in Perl 5.20.0

    Using this feature triggers warnings in the category "experimental::signatures".

    The ticket for this feature is [perl #13681] <https://github.com/Perl/perl5/issues/13681>.

Aliasing via reference
    Introduced in Perl 5.22.0

    Using this feature triggers warnings in the category "experimental::refaliasing".

    The ticket for this feature is [perl #14150] <https://github.com/Perl/perl5/issues/14150>.

    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 feature 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".

    See "'strict' mode" in re

The <:win32> IO pseudolayer
    The ticket for this feature 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 feature 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 feature 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".

    See also: "(*positive_lookbehind:pattern)" in perlre and "(*negative_lookbehind:pattern)" in perlre

  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

  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

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.