That sounds as though it might be the problem?
If you've got variable name clashes with the app itself, then there's a reasonable chance you're hurting its internals.
Unless such names are documented ways of interacting with the app, it seems like poor design. I would have thought they could have scoped the names into packages and had a limited/no lexical scope over your code.
The my $x if 0; construct is a bad (and unreliable in that's its behaviour may change in different versions of perl) way of generating what C programmers know as a static variable, i.e. one which maintains it's value across invocations of the function. This may not be what you're expecting, I don't know.
