@ngn yeah I knew there was a possible train there somewhere. Thanks!
Okay, now I'm trying to go tacit and I can't figure something out: 1⊥1,(!>×\)⌽⍳100 gives me the right answer, but (1⊥1,(!>×\)⌽⍳)100 doesn't. Dyalog says both group the same way, 1 ⊥ 1 , !> ×\ ⌽⍳ , so why are the results different?