Under normal CGI situations or FastCGI, what you suggest could be a real benefit.

Under mod_perl, however, because everything is kept in memory, it won't be as significant, as everything is loaded into memory and shared across scripts.

Will there be any difference? I don't know. Your best bet, in times like this, is to do a realistic benchmark of your exact system, and see if there's a difference, if it's that important to you.