You might like to check out Apache::SubProcess which does not seem too well documented, but I am looking at using it as a way to do the same from within a mod_perl environment.

The module overrides system() and creates a process from within perl which I believe is completely detached from the calling program. In mod_perl, if you fork() you can destroy the gains you made by using mod_perl in the first place, and so encapsulation in a perl module is recommended. If you are having trouble getting your process detached (memory-wise, and stdin/stdout/stderr-wise) why not try it out?

If anyone else has experience with Apache::SubProcess() I'd sure like to hear about it too! The mod_perl guide has a memo the author wrote that he needs to study it too!