bug#66050: Making perl-mode.el obsolete

[Stefan Kangas <stefankangas@gmail.com>]

Severity: wishist

I don't think it makes sense for us to spend our meager resources
maintaining two major modes for Perl.  I would like to gauge what people
think about obsoleting perl-mode.el.

Harald Jörg wrote previously on emacs-devel:

> Finally, perl-mode comes with its own list of ancient open bugs, many of
> those don't occur in cperl-mode.  I wonder whether the authors of these
> bugs would accept "use cperl-mode instead" as a workaround?
>
> At some time, it might make sense to merge those two modes into one.
> Perl continues to evolve, and upgrading two modes to support that
> doesn't seem to be an economic use of time.

    https://lists.gnu.org/r/emacs-devel/2020-10/msg01492.html

Here are some additional observations:

- cperl-mode.el sees more maintenance than perl-mode.el, in large part
  thanks to the efforts of Harald Jörg.

- The Perl community tends to favor cperl-mode over perl-mode.
  perl-mode is seen as lacking in features compared to cperl-mode, and
  no significant development has taken place to bridge the gap.

- cperl-mode.el used to be maintained outside of Emacs, but this is no
  longer the case.  All relevant development has been merged into and
  takes place in emacs.git.

- Perl, while historically important to hacker culture and still widely
  used in some quarters (e.g. Debian), is seeing much less use today
  than it used to.  This will negatively affect the amount of help we
  can expect with maintaining these modes from others.

- Instead of maintaining perl-mode.el, I'd rather see that people worked
  on a new perl-ts-mode.el.  From a web search, more than one treesitter
  grammar exist; I have no idea which one is the most promising or how
  mature any of them are.