[ Sequence ] replace: [ Number ] length: [ Number ] with: [ Sequence ]

☞ x ≔ Sequence ← 1 ; 2 ; 3 ; 4 ; 5.
☞ z ≔ Sequence ← 9.
☞ y ≔ x replace: 2 length: 1 with: z.
✎ write: y, stop.
Sequence ← 1 ; 9 ; 3 ; 4 ; 5