cperl-mode.el: Bring cperl-short-docs up to Perl 5.38.

cperl-mode.el: Bring cperl-short-docs up to Perl 5.38.

* lisp/progmodes/cperl-mode.el (imenu-max-items): declare the
variable to silence an elint warning.
(cperl-short-docs): Reorder function description to match Perl's
perlfunc documentation.  Add missing shortdocs from perlfunc.
Delete entries for operators which don't exist any more (EQ, NE
and friends).  Shorten docstring lines to 80 chars or less.