Perl pragma for deprecating the inclusion of a module in 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.
