Reported by lsf37 on 2006-04-22 13:08 UTC
in flex special characters lose their "special" meaning
inside a character class, with special-case syntax for
including square brackets themselves:
flex: [][]
JFlex: [][]
Note also that [] and [^] are illegal in flex. Also,
["] vs. ["] and I'm guessing the backslash itself (not
tested).

(reported by Dimitri Maziuk)