This is indeed a cool module and teaches me once again never to underestimate CPAN.
For many a source filter trying to hide source code this might be the breaking point.
Not so for the one I'm looking at, it croaks 'bad encryption format' -- in the Filter::decrypt of Paul Marquess there are magic numbers checked at certain locations in the encrypted source text to verify it has not been altered, and I think this is also the culprit for Filter::ExtractSource not working here.