I don't know about the 2+2 = 5 scenario (and wouldn't be wasting my time with one-liners from ranDoms) but I have never had a problem differentiating between 'play punishment' and 'real'. His disappointment is enough punishment for me so that I will remember not to do it again. Him withholding his attention from me or the words 'you disappoint me' would hurt more than any physical punishment he would want to inflict on me anyway.