cperl-mode "fatigue"

[Da Witch]

I've noticed that sometimes, especially after I have been editing a
buffer for a long time, or if I try to use "qw( ... )", cperl-mode
begins to show signs of "fatigue" (for lack of a better word).  For
example, syntax-based highlighting stops, and everything I type
appears in the default foreground text color; or else everything
appears in the color reserved for quoted strings.

Is there a way to fix this problem?

Thanks,

hk


PS: How can I figure out what version of cperl-mode I have?  Our
system has the cperl-mode.elc file only, and I don't know how to
determine the version from it.