in reply to
To taint or not to taint?
In a nutshell, Taint Mode is a collection of specific restrictions in Perl that collectively help you to write safer scripts by forcing you to think more carefully about how your script uses information. Specifically, it will prevent you from using or relying on data that was provided from outside the script within any action that will in turn affect something else outside of your script--unless you take specific steps to "clean" that data, first.
Have a look at "Introduction to Perl's Taint Mode" at http://www.webreference.com/programming/perl/taint/ for a better understanding.