:post run = "after error"

:l = [1,2]

1,2: {l}

~ l.insert(3)

1,2,3: {l}

§ a

~ l.insert(4)

1,2,3,4: {l}

§ b

~ l.insert(5)

1,2,3,4,5: {l}

~ error("cancel merge")

$ after error
	1,2,3,4: {l}