[Haskell-cafe] Physical equality

Is there in Haskell a non monadic function of type a -> a -> Bool which test for physical equality of two values? It would return True if only if both values are the same object in memory. For instance: value1 = "good" value2 = "good" eq value1 value2 => False value1 = "good" value2 = value1 eq value1 value2 => True Romildo