[1 J^P$L$$
J <.-Z; .,(S,$ -D .)FX1 @F^B $K :L I $ G1 L>$$
(where ^B means `Control-B' (ASCII 0000010) and $ is actually
an alt or escape (ASCII 0011011)
character).
In fact, this very program was used to produce the second,
sorted list from the first list. The first hack at it had a bug: GLS (the author) had accidentally
omitted the @ in front of F^B, which as
anyone can see is clearly the Wrong
Thing. It worked fine the second time. There is no space
to describe all the features of TECO, but it may be of interest
that ^P means `sort' and J<.-Z;
... L> is an idiomatic series of
commands for `do once for every line'.
In mid-1991, TECO is pretty much one with the dust of history,
having been replaced in the affections of hackerdom by EMACS. Descendants of an early (and
somewhat lobotomized) version adopted by DEC can still be found
lurking on VMS and a couple of crufty PDP-11 operating systems,
however, and ports of the more advanced MIT versions remain the
focus of some antiquarian interest. See also retrocomputing, write-only language.