The preacher buys a parrot

A preacher is buying a parrot.

"Are you sure it doesn't scream, yell, or swear?" asked the preacher.

"Oh absolutely. It's a religious parrot," the storekeeper assures him.

"Do you see those strings on his legs? When you pull the right one, he recites the lord's prayer, and when you pull on the left he recites the 23rd Psalm."

"Wonderful!" says the preacher, "but what happens if you pull both strings?"

"I fall off my perch, you stupid fool!" screeched the parrot.