perlexperiment - A listing of experimental features in Perl

- NAME
- DESCRIPTION
  - Current experiments
  - Accepted features
  - Removed features
- SEE ALSO
- AUTHORS
- COPYRIGHT
- LICENSE

# 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 #119317].

Pluggable keywords

  The ticket for this feature is [perl #119455].

  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 #119451].

  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 #121481].

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 #122947].

  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 #123630].

  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 #119453].

  See also 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 #128654].

  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 #116487].

Unicode in Perl on EBCDIC
Script runs

  Introduced in Perl 5.28.0

  Using this feature triggers warnings in the category `experimental::script_run`.

  See also: "Script Runs" in perlre

Alpabetic assertions

  Introduced in Perl 5.28.0

  Using this feature triggers warnings in the category `experimental::alpha_assertions`.

  See also: "Extended Patterns" 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 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

## 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.

perlexperiment - A listing of experimental features in Perl