experimental(3pm)
NAME
experimental - Experimental features made easy
VERSION
version 0.016
SYNOPSIS
use experimental 'lexical_subs', 'smartmatch';
my sub foo { $_[0] ~~ 1 }
DESCRIPTION
This pragma provides an easy and convenient way to enable or disable
experimental features.
Every version of perl has some number of features present but
considered "experimental." For much of the life of Perl 5, this was
only a designation found in the documentation. Starting in Perl
v5.10.0, and more aggressively in v5.18.0, experimental features were
placed behind pragmata used to enable the feature and disable
associated warnings.
The "experimental" pragma exists to combine the required incantations
into a single interface stable across releases of perl. For every
experimental feature, this should enable the feature and silence
warnings for the enclosing lexical scope:
use experimental 'feature-name';
To disable the feature and, if applicable, re-enable any warnings, use:
no experimental 'feature-name';
The supported features, documented further below, are:
array_base - allow the use of $[ to change the starting index of @array
autoderef - allow push, each, keys, and other built-ins on references
lexical_topic - allow the use of lexical $_ via "my $_"
postderef - allow the use of postfix dereferencing expressions, including
in interpolating strings
refaliasing - allow aliasing via \$x = \$y
regex_sets - allow extended bracketed character classes in regexps
signatures - allow subroutine signatures (for named arguments)
smartmatch - allow the use of ~~
switch - allow the use of ~~, given, and when
Ordering matters
Using this pragma to 'enable an experimental feature' is another way of
saying that this pragma will disable the warnings which would result
from using that feature. Therefore, the order in which pragmas are
applied is important. In particular, you probably want to enable
experimental features after you enable warnings:
use warnings;
use experimental 'smartmatch';
You also need to take care with modules that enable warnings for you.
A common example being Moose. In this example, warnings for the
'smartmatch' feature are first turned on by the warnings pragma, off by
the experimental pragma and back on again by the Moose module (fix is
to switch the last two lines):
use warnings;
use experimental 'smartmatch';
use Moose;
Disclaimer
Because of the nature of the features it enables, forward compatibility
can not be guaranteed in any way.
AUTHOR
Leon Timmermans <leont@cpan.org>
COPYRIGHT AND LICENSE
This software is copyright (c) 2013 by Leon Timmermans. This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.
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