written - and presumably performed - by Guy L. Steele Jr.
It is the cornerstone
of Donald Knuth
's fascinating article The Complexity of Songs
I'm not quoting its lyrics - being opposed to that, but feel free - but the song relates how a hacker used telnet to get to another CPU and knew he could quit whenever he wanted to by typing control up-arrow q, then repeats this process recursively. If you have ever used nested telnet sessions and its escaped escape sequences, you will figure out how this relates to the complexity of songs.
This was 20 years ago; today, 'up-arrow' is 'right hook'; besides, we use slogin and tilde-dot now. The complexity hasn't changed, though.