Haskell exceptions which are explicit in the type signature

 This package provides a library for the Haskell programming language.
 See http://www.haskell.org/ for more information on Haskell.
 .
 This library provides synchronous and asynchronous exceptions which are
 explicit in the type signature. The first ones are very similar to Either
 and Control.Monad.Error.ErrorT. The second ones are used for
 System.IO.readFile and System.IO.hGetContents.