Provided by: perl-doc_5.34.0-3ubuntu1.3_all 
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
Using this feature triggers warnings in the category "experimental::refaliasing".
The ticket for this experiment 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 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>.
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]
<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
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>"
Sébastien 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.