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 1975 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.
It is possible that this was intended as
tribute to a less colorful use of the same image in Robert Heinlein's
influential 1961 novel Stranger in a Strange
Land. See also hack mode and
on the gripping hand.