"[verbs] get forked and hooked until you go insane trying to track it all"
J comes with a Qt IDE, which has a function "dissect" that displays a graphical parse tree of an expression.
load 'debug/dissect'
dissect '(+/ % #) ? 10 $ 100'
Thanks! I haven't touched J in about ten years -- and I never used dissect -- and I never did anything serious in it, just about thirty project euler problems for fun.
That should have an ASCII art alternative too.