Oh, I wouldn't go so far as to call it evil, but yeah I agree it's not exactly Ruby.
Using Lemon is an interesting choice. Our product is very parser-heavy, and we've played with most of the mainstream libraries. I'm not sure what the win is with Lemon over Racc.
I was going to say-- without Modules, Procs, or Blocks, it's not really Ruby, now is it? :P Still, a ~2000 sloccount makes this a neat and succinct little piece of software, so grats to the author.