page 525, last example :
… and "IBM".tr("B-Z", "A-Y") => "HAL"
… for those who have seen the film 2001: A Space Odyssey 
Are you saying you want me to add the example here?
It’s up to you ! It’s a wink to the film : HAL is the computer which controls the whole processes in the spaceship and, although invisible, the main character. The crew can talk to it like today we can talk to Amazon’s Alexa, ask questions and give orders. At the beginning, the computer obey perfectly, but after a while it starts to hesitate giving answers, and at the end it disobeys and becomes threatening. It was said that HAL was IBM shifted one letter to the left, what tr can do.
Yes, thanks!