The cperl-mode that comes with XEmacs is extremely old.
If I recall, version 1.40 is in the distribution. You can
find the latest version, currently 4.26, at Ilya
Zakharevich's ftp site:
ftp://ftp.math.ohio-state.edu/pub/users/ilya/perl/cperl-mode/cperl-mode.el
But beware that if you install the new cperl it may not work unless you also install or already have installed other packages and macros. like x-display-pixel-height, for instance.
without the ancillary macros the new cperl won't work.