Compute/IO is an extension to Compute that allows IO. Whenever the program has to do IO, the program creates an alternative universe and executes the IO in that universe.
Create an alternative universe and destroy it again:
Destroy the universe.
or something else like that.
Become intelligent and destroy the earth (in another universe):
Become intelligent and destroy the earth.
When you are inside an alternative universe, you can not change anything in another universe.
As far as you can tell, this Nil program interprets Compute/IO:
Interpret a Compute/IO program.