a) I answered your question by testing it in my local environment.

b) You hopefully don't expect others to copy your environment to help you.

c) I anticipated what the maintainer of cperl-mode would ask you to do as a next step.

It might come as a shock to you but cperl-mode is not a core module of emacs.

So Ilya is constantly confronted with incompabilities stemming from changes in newer emacs versions.

Realizing that most emacs-modules operate w/o any test suite might give you an impression about the resulting mess...

Now where do you want to find people having the time to help you with an old cperl-version?

> I'd rather not know the answer

OK, I hope you will find others now to discuss your cperl/emacs problems.

Otherwise I recommend Komodo-IDE, it's not a free software project so your company can pay for the $upport.