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Apply 𝔽 to the cells of the arguments at depth given in 𝕘. Negative numbers count down from the top level and non-negative ones from the bottom up.
1⊸↓⚇1 ⟨⟨1,2,3⟩, ⟨4,5,6⟩⟩
1 ↓⚇1 ⟨⟨1,2,3⟩, ⟨4,5,6⟩⟩
(+´↕)⚇0 ⟨2,4‿7,3⟩ # Implements pervasion