Whenever I upgrade running processes, I check lsof. Specifically, lsof | grep DEL.*lib | less -S (as root). Any process there (the first column) needs to be considered for restarting at your earliest opportunity. Generally, this includes a lot of my desktop apps which I worry about less, since I just log out and log back in and they'll all be reloaded (sometimes, this includes kwin, or even X, which pretty much necessitates this approach). Others are simply a restart of their file in /etc/init.d.

This applies to all processes, not just perl. It just so happens that it will probably solve your perl question, too, as the perl executable is one of the open files that will be missing.