Perl philosophy says "laziness is a virtue". Often being lazy means doing a little bit of work up front to save a lot of work later. Two cases in point (and they are related): preview your nodes and use strictures. Both give you a heads up about nasty stuff down the track.

In this case taint checking ought be added to the strictures recommendation.

You may find that MIME::Lite or one of the many other email manipulating modules make editing headers (in particular) and managing email in general much easier.