In fact, it's a perlism I am extremely fond of. I can easily see someone in a design discussion saying, What? We don't need that informal, random parsing trouble. It's just numbers. If you can't read numbers, you shouldn't be programming. That underscore has saved me many hours of reading comprehension and probably a hundred hours of chasing bugs and mistakes in code. Update: and scratches on my monitor as I try to count digits with pen or ruler. :P