In reply to trentbuck(a)gmail.com (Trent W. Buck):
Graeme Cross <gcross(a)fastmail.fm> writes:
I do not believe that is possible. AFAICT, this ABNF
snippet from RFC
5322 (p12) is irregular:
My formal-language theory is a bit rusty, but, indeed, you can't
recognize context-free languages (having nesting), using regular
expressions (even extended with backreferences, as they usually
are in practice).
-- Smiles, Les.