Thank you very much for your support!

I am sure that your analysis regarding the comparison operators is correct. perlvar states that the group ids actually are strings (and thus should be compared using eq in Perl) and that user ids are numbers (and thus should be compared using ==).

That they use an array one time and two separate variables the other time does not worry me too much. Of course I agree with you that there should be much more comments.

The main problem is that dropping privileges is seemingly is a no-op, but I am quite sure that actually it isn't one. For the life of me, I don't understand the sense, and even worse, I have conducted a lot of tests with setgid / setuid flags, but couldn't construct a situation where the code under # Drop privileges was not a no-op.