From The Free On-line Dictionary of Computing (19 January 2023):
Lex
1. <tool> A lexical analyser generator for Unix and its
input language. There is a GNU version called flex and a
version written in, and outputting, SML/NJ called ML-lex.
A version, by David Poole at Montana has been retargeted to
Turbo Pascal, (ftp://iecc.com/pub/file/lyprg.zip).
["Lex - A Lexical Analyzer Generator", M.E. Lesk, CS TR 39,
Bell Labs, Oct 1975].
2. <language, specification> The lexical specification
language for COPS.
["Metalanguages of the Compiler Production System COPS",
J. Borowiec, in GI Fachgesprach "Compiler-Compiler", ed
W. Henhapl, Tech Hochs Darmstadt 1978, pp.122-159].
(2000-11-15)