I think you don't need to worry about putting stuff in a BEGIN block as you've indicated -- I believe that mod_perl is clever enough to do what you want it to.

If you edit something, an old version of the script might still be in memory. Years ago I would do an apachectl graceful to get Apache to pay attention to the change I'd just made. Sometimes that wouldn't work, and I'd have to rename the file, press refresh a couple dozen times until I got the "Unknown module" error, then restore the file and continue testing.

I think you can still call exit as you're suggesting -- to stop execution of that instance of the code. But a test should be fairly easy to set up.

I wish I could provide more information, but my experience comes from a period of frantic web development in 1998-2000, and some more recent 'dabbling' that has re-introduced me to mod_perl without actually giving me time to get really familiar with it.

Good luck!