This effect is a very simple one. It allows the delayed execution of
computations and it can serve as some sort of overall IO
effect.
Two methods are available to execute this effect:
runEval: Eff[U, A] to just execute the
computations
attemptEval: Eff[U, Throwable Either A] to execute
the computations but also catch any Throwable that would be
thrown
`> 2`