“The mother of all my films,” according to Abbas Kiarostami, starts out as a breezily observed anecdote about a boy wending his way home through Tehran alleys carrying a loaf of bread. Variations on both the boy and the old man he sees and begins to follow will factor into future Kiarostami films, as will the use of “dead time,” the journey structure, and the poetic articulation of space. The final scene, involving a dog and a door, ends things on a note of wry ambiguity.