⍟)𝔽⍟𝔾 𝕩, 𝕨 𝔽⍟𝔾 𝕩: RepeatApply 𝔾 to 𝕨 and 𝕩, then apply 𝔽 to 𝕩 that many times. If 𝕨 is given, use it each time as a constant left argument.
If 𝔾 returns an array, give 𝔽⍟𝕩 for each of its elements.
1 +⍟⊢ 4 8 1 +⍟1‿2‿3 4 ⟨ 5 6 7 ⟩ 3 ∾⍟{≠𝕩} ⟨4,5,6⟩ ⟨ 3 3 3 4 5 6 ⟩