Keeping an interpreter resident in memory is necessary for real speed with mod_perl, just as it is with PHP or Java servers. If you have enough traffic that you need to decouple the network I/O, using a front-end server works fine, or you could use more experimental options like lingerd. The front-end web server passing requests to a dynamic back-end server is an approach used by many tools, from FastCGI to high-end commercial application servers. The two servers happen to communicate over HTTP in this case, but the concept is nearly universal.