Pulsed laser control of photodissociation in the strong and the weak coupling regimes is analyzed. Simple pulse shaping conditions are derived and are given explicitly in the weak coupling regime. Implicit equations in the strong coupling regime are also derived. Short, shaped pulses, yielding optimal control, are shown to work due to quantum interference among routes to the same final energy. This is contrary to the prevailing view that the role of a short pulse is to be fast enough so as to "beat the process of intramolecular vibrational redistribution (IVR)".