Thanks for the background flexvault, I doubt I would have posted anything had I known you were doing something with database keys. I thought you might be writing some sort of diff routine for a homebrew editor or some such. (I should have checked you out anyway to see that you've way too much history and mojo to need to be told about iterators.)
I looked more at JavaFan and jwkrahn's solutions than your initial statement of the problem, so overlooked your use of the bytes pragma. I guess I'm conditioned to look for the -M and -m options. I've never used the bytes module, which seems to make all strings just byte vectors. Modding out by endianess, do you think there's some sort of bit-wise C idiom out there to capitalize on the fact one and only one of ($s1 & ($s1 ^ $s2)) or ($s2 & ($s1 ^ $s2)) will have the "high order bit"? You might be able to get away from using a regexp by, e.g., craftily using bit shifts. But I'm unfamiliar with issues such as if using numerical ordering in database keys impacts performance with things that might have a different lexicographic ordering.
I don't think you need to apologize for using "modern Perl" in a general sense. chromatic puts that include at the top of his responses in PM and it's good PR for his excellent book, Modern Perl 2011-2012 Edition, but knowledgeable folk such as yourself are given lots of latitude by students such as myself, who learn a lot whenever you produce a "modern Perl" example.