cperl-problems is a variable defined in `cperl-mode.el'.
Its value is

Description of problems in CPerl mode.
Some faces will not be shown on some versions of Emacs unless you
install choose-color.el, available from

`fill-paragraph' on a comment may leave the point behind the
paragraph. It also triggers a bug in some versions of Emacs (CPerl tries
to detect it and bulk out).

See documentation of a variable `cperl-problems-old-emaxen' for the
problems which disappear if you upgrade Emacs to a reasonably new
version (20.3 for Emacs, and those of 2004 for XEmacs).