[Haskell-cafe] Control.Concurrent.STM.old?

Does the 'old' function referenced in the SPJ and Tim Harris data invariants paper stil exist? It is of type STM a -> STM a and allowed invariants to compare old TVar values with new ones. I can't find it in any of the Haddocks or the code (and the 'check' funciton is not commented in the Haddock). Tom