mod_perl is a heckuva lot more than a dynamic website speedup hack. It gives you hooks into every phase of the Apache request lifecycle (authentication, URI translation, content, etc. etc. etc.), which offers you ludicrous amounts of power. I don't think any JSP engine gives you all that, either a standalone JSP-type server (I've used the Apache project's Tomcat engine in this capacity a bit) or one that's embedded into Apache w/mod_jserv.

So if these hooks into Apache are something you'd like to have in your toolkit, mod_perl seems to be ahead on this.

(Any of those more familiar with Tomcat etc. feel free to correct me on this point, I'm interested too).

Philosophy can be made out of anything. Or less -- Jerry A. Fodor