«)« 𝕩: Nudge BackRemove the first element of 𝕩, add a cell of fill values to the end of the first axis of 𝕩.
78 « 1‿2‿3 ⟨ 2 3 78 ⟩ « 1‿2‿3 ⟨ 2 3 0 ⟩ « 3‿3 ⥊ 9 ┌─ ╵ 9 9 9 9 9 9 0 0 0 ┘
𝕨 « 𝕩: Shift BeforeRemove the first ≠𝕨 (length) major cells from 𝕩, join 𝕨 to the end of 𝕩. Ranks must match.
8‿5 « 1‿2‿3 ⟨ 3 8 5 ⟩ a ← 3‿3 ⥊ 9 1‿2‿3 « a ┌─ ╵ 9 9 9 9 9 9 1 2 3 ┘