Hi,
Good luck with this project.
Once you have a test environment either on your unix box or PC, I would take a copy of the code and start going through it line by line, making LOTS of comments/note as you go. You do not have to become a Perl Geru by October 31st just a geru of your program.
To find out how lines or sections work try pulling them out to small test scripts and pass them variables which you feel will test the code. The -w and use strict should be used here as well. Their messages are very useful.
Hope this helps,