Quoting Tom Lane <tgl@sss.pgh.pa.us>:
...
> What is flex 2.5.23? AFAICS 2.5.4a is still the newest release
version
> (there's nothing newer on the GNU mirrors, nor according to
freshmeat).
>
flex is non-gnu, the official site is afaik :
http://astro.temple.edu/~john43/flex/
regards
Bartosch