The tiny comma can carry huge significance. The following story, inflicted on a recent gathering of San Francisco State University film students, illustrates its power to change meaning:

A panda goes into a cafe and orders a bamboo sandwich. He finishes the sandwich, pulls a BB gun from his backpack, peppers the ceiling with birdshot, and walks out the door.
A fellow diner runs after him and asks why the mayhem.
"I'm a panda," explains the panda.
"So?" persists the other diner.
"Look it up in the dictionary," says the panda--"'Panda: a short-tailed mammal that eats, shoots, and leaves."