I think that I have a pretty good understanding of basic perl and programming theories.

If you think 'FILE.gpg' and 'FILE.pgp' are "identical data", then I would have to dispute your claim.

Furthermore, do you realize that m/\Q\E/ matches everything, and thus that

  $expected_sender = '';
  if ( $signer =~ /\Q$expected_sender\E/ )
[download]

will always be true?

It is entirely unclear why/how your section 1 and section 2 could be related. Since you "know" that they are, you have useful information which you're not sharing. Do you want us to help, or not?

jdporter
The 6th Rule of Perl Club is -- There is no Rule #6.