Suggestion: Make cperl-mode.el an ELPA :core package

[Harald Jörg]

Hello all,

Within the next weeks we expect the release of Perl 5.38.  This version
includes some changes which should be supported by CPerl mode.  Most
notably, there will be a builtin object system with keywords "class" and
"method", which are relevant for syntax highlighting, imenu, and
indentation.

I am currently working on adding these to cperl-mode.el.  But these
will, in the normal course of action, not be released before Emacs 30
comes out.  Therefore I'd like to make cperl-mode.el available via ELPA.

If I understand it correctly, then the file can continue to be developed
in the Emacs repository, if it is flagged as ":core".  cperl-mode.el
would need a "Version:" header so that it can be released independent of
Emacs versions.  So, if the version in cperl-mode.el is changed, ELPA
will deliver the new version.  Are there conventions where to start?
Historically cperl-mode.el had its own versioning, based on an upstream
which no longer exists.  This ended with version 6.2, the variable
cperl-version has been obsoleted as an own variable in Emacs 28.1.  I
think it would make sense to start from there and release the first ELPA
version as 7.0.

I am regularly running tests for cperl-mode.el in older Emacs versions
(and have added a few compatibility helpers).  Are there any more
changes to do?

-- 
Cheers,
haj