If "understanding Perl" isn't a choice, then it looks like you've got three choices.

• Modify your application where you meant zero but have undef.
• Use a hack like redefining undef via some Tie method, for those regions of your application where it's important.
• Find something other than Perl to do your work.

I mean, not to be rude or anything, but have you considered that there's a LOT of Perl code out there which would break badly if undef and zero were the same concept?

If you're using any modules in your application, they're going to be hosed. If your code is so insular that you're not using other people's modules, then it should be pretty straightforward to rewrite the code so it agrees with such fundamental Perl values.