Man1 - perlexperiment.1perl

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

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

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).

1. Introduced in Perl 5.005 Removed in Perl 5.10
2. Introduced in Perl 5.005 Moved from Perl 5.9.0 to CPAN
3. Introduced in Perl 5.6.0 Removed in Perl 5.9.0
4. GetOpt::Long Options can now take multiple values at once (experimental) :: Getopt::Long upgraded to version 2.35 Removed in Perl 5.8.8
5. The -A command line switch Introduced in Perl 5.9.0 Removed in Perl 5.9.5
6. Moved from Perl 5.10.1 to CPAN
7. The experimental legacy pragma was swallowed by the feature pragma. Introduced in Perl 5.11.2 Removed in Perl 5.11.3
8. Using this feature triggered warnings in the category experimental::lexical_topic. Introduced in Perl 5.10.0 Removed in Perl 5.24.0
9. 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
10. “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