experimental(3perl)    Perl Programmers Reference Guide    experimental(3perl)

       experimental - Experimental features made easy

       version 0.016

        use experimental 'lexical_subs', 'smartmatch';
        my sub foo { $_[0] ~~ 1 }

       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;

       Because of the nature of the features it enables, forward compatibility
       can not be guaranteed in any way.

       Leon Timmermans <leont@cpan.org>

       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.

perl v5.26.1                      2020-10-19               experimental(3perl)
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