the dnalen function can't detect point mutations, so that wouldn't work. And the junk DNA would only detect mutations in the junk DNA, not the important DNA, right?
So what I find most appealing is the third option, but I wasn't sure how to do that. DB uses reverse polish notation, but I haven't been able to find push/pop commands, so I'm not exactly sure how to do that... Could you show some pseudocode, if you don't mind?