Hmmm ... there's plenty of modperl info pages: perlmonks is not a replacement for google.

Where's the code? Just running as the user apache doesn't necessarily mean it will run well under cgi or modperl. I can envision two scenarios as to why this is failing: 1, relative pathing - your pwd is not where you think it is; and 2, suexec is being used and apache isn't the effective user.

But you forgot one very important piece of information -- how is the script failing (file doesn't exist, user doesn't have permissions)?