Nice. You remembered that `/` takes a vector left argument. We can do a bit of algebraic manipulation and factor out the common parts:
1. Ravel on both arguments can be performed by Over (⍥): `(Contents > 5) /⍥, Contents`
2. Make into a train: `(>∘5 /⍥, ⊢) Contents`, but...
3. Unfortunately, since `/` is both an operator and a function, we have to force it to parse as a function in trains: `(>∘5 ⊢⍤/⍥, ⊢) Contents`