---------------------------
-#if __GLASGOW_HASKELL__ < 609
-tryM :: IOEnv env r -> IOEnv env (Either Exception r)
-#else
tryM :: IOEnv env r -> IOEnv env (Either IOException r)
-#endif
-- Reflect UserError exceptions (only) into IOEnv monad
-- Other exceptions are not caught; they are simply propagated as exns
--