MIME::Tools has become an important component in a number of antivirus scanners and the like in mail gateways. In this sort of usage, you can't assume well formed MIME input. Some viruses deliberately mess with the MIME formatting in order to evade detection. IF you're dealing with messages you can reasonably expect not to be maliciously constructed, there should be no problem.
For more information on the problems, see
The Current release version of MIME::Tools (5.411a) hasn't been updated since 2001, and the author is advertising that he's looking for someone else to take over MIME::Tools and MIME::Lite. The makers of MIME::Defang have been releasing their own version. You can get it at