I was largely joking. Even though the capability is there, it is not computationally practical nor possible to accomplish such a feat for any sufficiently complex programme.

In the most extreme case, attempting to run a complex Prolog programme backwards will result in an increase in entropy levels in the universe to such an extent that it will cause an instant cold (or hot) death of our universe, and life as we know it will perish momentarily (another tongue in cheek joke).