ghc 6.0.1 win98 System.system too successful?

Shouldn't this return something other than ExitSuccess, occasionally?
Cheers,
Claus

PS. the first error message says "command not found"
PPS. this is from within cygwin's bash

$ ghci
   ___         ___ _
  / _ \ /\  /\/ __(_)
 / /_\// /_/ / /  | |      GHC Interactive, version 6.0.1, for Haskell 98.
/ /_\\/ __  / /___| |      http://www.haskell.org/ghc/
\____/\/ /_/\____/|_|      Type :? for help.

Loading package base ... linking ... done.
Prelude>
Prelude> System.system "fail" >>= print
Befehl oder Dateiname nicht gefunden.
ExitSuccess
Prelude> System.system "diff ClassIn1.hs ClassIn1_TokOut.hs" >>= print
7c7
< class Reversable a where
---
> class MyReversable a where
11c11
< instance Reversable [a] where
---
> instance MyReversable [a] where
ExitSuccess
Prelude>