deprecate(3pm) Perl Programmers Reference Guide deprecate(3pm)
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(3).
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 v5.38.2 2023-11-28 deprecate(3pm)
perl 5.38.2 - Generated Sun Dec 15 15:02:52 CST 2024