bug#70948: 29.3; cperl mode hangs on comments like "#___"

[Eli Zaretskii <eliz@gnu.org>]

> From: Harald Jörg <haj@posteo.de>
> Cc: 70948@debbugs.gnu.org
> Date: Thu, 16 May 2024 16:43:24 +0000
> 
> Eli Zaretskii writes:
> 
> > Please note that, barring any unforeseen emergencies, there will be no
> > more Emacs 29.x releases.  So I'm not sure the effort of making the
> > emacs-29 branch behave better in this matter is justified.
> 
> I understand!
> 
> My suggested course of action would be like this:
> 
> 1) Make cperl-mode.el from the master branch work with older Emacsen
>    (again).  This needs a one-line fix.
> 
> 2) Work around the inefficient rx expansion in the master branch.  This
>    seems to be another one-line fix in which I replace a rx sequence by
>    the expansion it gets in master (explanatory comment omitted here):
> 
>      (defconst cperl--basic-identifier-rx
>    -    '(sequence (or alpha "_") (* (or word "_")))
>    +    '(regex "[_[:alpha:]][_[:word:]]*"))
> 
> 3) Close the bug report, noting it has already been fixed in master.
>    Explain that users can use cperl-mode.el from the repository as a
>    drop-in replacement in Emacs 27 or newer if they are affected by the
>    bug.

SGTM, thanks.