≠\ is an awesome trick. You might also like {2 | (1+⍳≢⍵) (⊣ - ⌈\⍤×) ~⍵}` for `⎕IO←0 for detecting which escape characters are themselves escaped. This is translated from BQN: https://github.com/mlochbaum/BQN/blob/master/md.bqn#L53

This last is more compactly expressed as <\ when you have left to right folds which (unfortunately) APL does not.