Shooting yourself in the foot
Picked up from file:///usr/share/doc/pugs-doc/other/shot_in_the_foot
(from http://lincoln.midcoast.com/~del/task.html )
(from http://santiago.mapache.org/humor/shootfoot.html )
All you have to do is calculate the value of the shoot function on foot. (You did define shoot, didn't you?)
You pick up an object which assures you it provides the function of a gun. You load the gun with something that functions like a bullet, but are not sure whether you actually loaded it or whether it will load itself when you try to use it or check the chamber. You point and fire the gun at your foot, or something which functions like a foot, but because you did not specify which foot, the interpreter fires the bullet in each of two parallel universes. You are not sure whether or not you hit your foot, or indeed which foot you fired at, but you decide that you don't currently care. You carry on doing something else and forget what happened. Later, when you go to get a bite to eat, or at least find something which provides the function of being bitten for the sake of nutrition, you notice a parrot grab the gun, load it, and shoot you in both feet - both hit the mark, but only one leaves a bullet wound because the operation was atomic.