Thank you so much for getting me an answer in 15 minutes to something I'd already spent hours on. You have inspired me to start using strict and warnings ... well my code is around 600 lines already and I should be able to wrap it up now ... I'll use those on my next project.
Your maintenance challenges down the road will be much fewer AND simpler if you deal with the problems strict and warnings complain about now, while you still remember what your code means...
(You should also add documentation and tests, seriously. But making things strict/warnings clean is a good start)
Bzzzt - wrong answer. Add strictures now. You've already seen the benefit - two errors detected in about 30 lines of code, so there could be about 38 more errors to find in the remaining 570 lines which is about another two weeks of possible debugging time saved! ;)