Keeping a lot of state in your head while modifying a

program. "Don't bother me now, I'm juggling eggs", means that

an interrupt is likely to result in the program's being

scrambled. In the classic first-contact SF novel "The Mote in

God's Eye", by Larry Niven and Jerry Pournelle, an alien

describes a very difficult task by saying "We juggle priceless

eggs in variable gravity." See also hack mode.