CPerl behaves differently on XP in 21.3 and 21.3.50.1

[Ekkehard Goerlach]

I have parallel installation of Emacs 21.1 and 21.3.50.1 (nqmacs on
sf). Both Emacsen use the same .emacs and site-lisp directory which
contains the (only) cperl-mode.el V5.0

If I open a perl file in both emacsen, the font-locking is slightly
different. POD documentation, for example, does not show up in comment
face in the 21.3.50.1 and the following code 

my $revision = (split(/ /,'$Revision: 1.48 $'))[1];

looks fine in 21.3 but for the more recent emacs I have to insert an
extra space in the revision string:

my $revision = (split(/ /,'$Revision: 1.48 $ '))[1];

Is there some customizaton possible to get the same font-locking in
both Emacs versions?

Thanks,
Ekkehard