"grue" is an irc bot developed in perl for Linux, which allows a group of people to play an Infocom/Z Machine game.

a fictional predator from the zork series of interactive fiction games by infocom

Grue and bleen are artificial predicates, coined as two portmanteaux of "green" and "blue" by philosopher Nelson Goodman in one of the seminal works in the philosophy of science, Fact, Fiction, and Forecast. The words are used to illustrate what Goodman calls "the new riddle of induction".

a creature that will eat you if you continue to walk around in the dark