--- Computation `getEnv var' returns the value
--- of the environment variable {\em var}.
-
--- This computation may fail with
--- NoSuchThing: The environment variable does not exist.
+-- | Computation 'getEnv' @var@ returns the value
+-- of the environment variable @var@.
+--
+-- This computation may fail with:
+--
+-- * 'System.IO.Error.isDoesNotExistError' if the environment variable
+-- does not exist.