unless package:universum

unless :: Applicative f => Bool -> f () -> f ()
universum Universum.Bool.Reexport
The reverse of when.
unlessM :: Monad m => m Bool -> m () -> m ()
universum Universum.Bool.Guard
Monadic version of unless. 
>>> unlessM (pure False) $ putTextLn "No text :("
No text :(

>>> unlessM (pure True) $ putTextLn "Yes text :)"