P.P.S. the guy who originally did this stuff has left the company, for some time now

Get in contact with that man -- is the best and cheapest advice there is.
You might not believe me, others probably will not believe you, but try anyway.

Update: Perl Medic: Transforming Legacy Code by Peter J. Scott is a book on the subject that's worth while.
The other Update is a link to the book: "Perl Medic: Transforming Legacy Code"