Here's when to use PHP vs JSP vs ASP vs Perl
If your priorities are:
Low cost of deployment
fast development of site
ease of maintenence for smaller sites
simpler programming needs
working on slower older servers
and you don't mind
having a little less power and extensibilty for some things,
choose PHP
if they are:
extensibility
more powerful programming needs (such as server side multimedia processing, etc.)
ease of maintenence for larger sites
integration of logic into existing business systems.
and you don't mind
having to set up some complex stuff to get it running well for free and needing a slightly more powerful server and more dev time for smaller sites,
Choose JSP
if they are:
Making money
Being in demand in the job market
having a fair amount of similar power and a touch more speed than JSP in your applications
and you don't mind
feeding a monopoly, working on MS only platforms, paying dearly for the right to do so.
Choose ASP.
if you need:
Powerful applications that will be easy to develop
and don't mind
that they can NOT be involved in a high number of page views, or will have a REAL powerful server(s) to handle the CPU load of all the multiple processes (as opposed to efficient multithreading used in all the languages above)+ not separation of content/logic
choose PERL.
P.S Correct me Perl folks if I am wrong, your language is the one I have yet to delve into professionally and therefore know the least about, but having it run through CGI the single process per request thing is obviously bad for high traffic, especially on all but the lates Linux kernels where there are problems with the handling this due to stack problems(?). If there's a workaround correct me! I have heard great things about perl and its my next language to learn.