And don't forget to mention that using a reverse proxy will keep your server with a minimal number of mod_perl processes running, i.e., setup an Apache on port 80 (with mod_proxy activated) and redirect every *.pl requests (or all /cgi-bin request, for example) to your mod_perl enabled Apache on another port (81, for instance).

You'll be able to handle even more scripts per second because you will keep the mod_perl server busy only to process the request, and the transmission of the output will be a task for your light Apache on port 80, freeing it to handle another script request.
HTH.