deprecate

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

NAME
       deprecate - Perl pragma for deprecating the inclusion of a module in
       core

SYNOPSIS
           use deprecate;  # warn about future absence if loaded from core

DESCRIPTION
       This pragma simplifies the maintenance of dual-life modules that will
       no longer be included in the Perl core in a future Perl release, but
       are still included currently.

       The purpose of the pragma is to alert users to the status of such a
       module by issuing a warning that encourages them to install the module
       from CPAN, so that a future upgrade to a perl which omits the module
       will not break their code.

       This warning will only be issued if the module was loaded from a core
       library directory, which allows the "use deprecate" line to be included
       in the CPAN version of the module. Because the pragma remains silent
       when the module is run from a non-core library directory, the pragma
       call does not need to be patched into or out of either the core or CPAN
       version of the module. The exact same code can be shipped for either
       purpose.

   Important Caveat
       Note that when a module installs from CPAN to a core library directory
       rather than the site library directories, the user gains no protection
       from having installed it.

       At the same time, this pragma cannot detect when such a module has
       installed from CPAN to the core library, and so it would endlessly and
       uselessly exhort the user to upgrade.

       Therefore modules that can install from CPAN to the core library must
       make sure not to call this pragma when they have done so. Generally
       this means that the exact logic from the installer must be mirrored
       inside the module. E.g.:

           # Makefile.PL
           WriteMakefile(
               # ...
               INSTALLDIRS => ( "$]" >= 5.011 ? 'site' : 'perl' ),
           );

           # lib/Foo/Bar.pm
           use if "$]" >= 5.011, 'deprecate';

       (The above example shows the most important case of this: when the
       target is a Perl older than 5.12 (where the core library directories
       take precedence over the site library directories) and the module being
       installed was included in core in that Perl version. Under those
       circumstances, an upgrade of the module from CPAN is only possible by
       installing to the core library.)

EXPORT
       None by default.  The only method is "import", called by "use
       deprecate;".

SEE ALSO
       First example to "use deprecate;" was Switch.

AUTHOR
       Original version by Nicholas Clark

COPYRIGHT AND LICENSE
       Copyright (C) 2009, 2011

       This library is free software; you can redistribute it and/or modify it
       under the same terms as Perl itself, either Perl version 5.10.0 or, at
       your option, any later version of Perl 5 you may have available.

perl v5.30.0                      2023-11-23                  deprecate(3perl)