[goto11]

It would just mean that IO operations would happen in random order or not at all, due to the laziness of Haskell. E.g. if you call getLine twice with the same "world" argument, then it would presumably only be executed once. And if you don't "consume" the returned world state from an IO operation, then the operation would not be executed at all.

Haskell does allow you to do something like this with the unsafePerformIO "backdoor".

The documentation states: "If the I/O computation wrapped in unsafePerformIO performs side effects, then the relative order in which those side effects take place (relative to the main I/O trunk, or other calls to unsafePerformIO) is indeterminate"