This is a variant of the Flex fast lexical scanner. Flex was written in the early
1990s by Verne Paxson. This version has been modified by Thomas Dickey, so that
it conforms to ANSI C. It includes other improvements, but remains compatible with
Paxson's 2.5.4 release (as well as POSIX lex). See the NEWS file for details.

WWW: https://invisible-island.net/reflex/