This is a terrible, no good, very bad idea, which is probably really useful. It's rather like using awk for stuff that covers more than 10+ lines unless you really, really have to.
Thanks, hehe yeah it does seem a bit like writing over the inputs isn't really a great plan in general, except in rare cases where it's a total escape-hatch! (probably amazingly useful then!)
I think I mostly agree about the 10+ lines thing although I think I've written things nearly 20 lines (that aren't that crazy!) However there's that undergraduate AI course from 1997 that used it! They would've had loads of lines there I reckon!
The original url has rotted now, but here it is on archive.org:
