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>.

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

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>.

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>

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.

for loop with multiple iteration variables

Introduced in Perl 5.36.0.

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

This feature enables a parenthesized list of iteration variables for "for" rather than a single variable.

The ticket for this experiment is [perl #18744] <https://github.com/Perl/perl5/issues/18744>.

The builtin namespace

Introduced in Perl 5.36.0.

Using 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 is considered an experiment. Specific functions within it may also be experimental.

The ticket for this experiment is [perl #19764] <https://github.com/Perl/perl5/issues/19764>.

The defer block modifier

Introduced in Perl 5.36.0

Using this feature triggers warnings in the category "builtin::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] <https://github.com/Perl/perl5/issues/17949>.

Extra paired delimiters for quote-like operators

Introduced in Perl 5.36.0

Using this feature triggers warnings in the category "builtin::extra_paired_delimiters".

This feature allows for many non-ASCII pairs of mirroring delimiters, for example:

    my @array = qw« tinker tailer soldier spy »;

The ticket for this experiment is [perl #19765] <https://github.com/Perl/perl5/issues/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

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)