Beware: You should stick with the bundled cperl-mode version. Loading another version can cause strange problems.

see groups.google.com/group/gnu.emacs.help: fontification problem with PODs

Better update to the newest emacs, the cvs trunk of 23 has already cperl 6.2 included.

It's not necessarily caused by Ilya, the emacs-team is regularly changing details, even his code.