So, is there any way to determine whether a block of code is Perl code or not-code, or should I try something else?

POD doesn't define C<> and verbatim paragraphs as having to contain perl code so using them for program output, etc. is perfectly acceptable.

This means you're going to have to come up with some heuristics to guess whether something is/isn't perl - but that's not going to be 100% whatever you do I'm afraid.