On a more general level, all your PERL-scripts which run under mod_perl must be coded carefully, as they probably get only compiled once for a multitude of requests and therefore the old contents of variables my linger on long after they should have died under a non mod_perl run script.

The use of strict is not only recommended it is almost indispensable to guard against careless programming style.
That and make sure that you initialize all your variables (either explicitly or trough the use of my) as you cannot count on them being 'virgin'.

CountZero

"If you have four groups working on a compiler, you'll get a 4-pass compiler." - Conway's Law