Since no one else has responded, I will take a crack at it. Please correct me if I'm wrong. mod_perl caches the compilation of the Perl script. Thus, if the perl script runs once it will run faster the next time, because Perl doesn't need to compile it. This makes it comparably fast to C. What modules you are using should be irrelevant, as should how many system() calls you make, because all mod_perl is doing is caching the compilation.
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