measured the effect on nofib of changing OLD CODE to 'True', and got
zeros everywhere, but a 4% win for 'puzzle'. Very small 0.5% loss for
'cse'; turns out to be because our arity analysis isn't good enough
-yet (mentioned in Simon-nofib-notes.
+yet (mentioned in Simon-nofib-notes).
OLD comment was:
Even if it escapes a value lambda, we only