He might make sure he has a current cperl-mode. http://cpan.org/authors/id/I/IL/ILYAZ/cperl-mode/

Update: cpan only seems to have older versions up through 4.32. Newer versions are at http://math.berkeley.edu/~ilya/software/emacs/.

I can duplicate the problem on emacs 21.2 with cperl-mode 4.23, but people in the CB with versions 4.35 or 5.0 say it works for them.