Does anyone know of an O'caml rfc822 address parser?

`mmm', the O'caml web-browser has a simple date lexer, although its
not rfc822 compliant.

The ocamllex documentation doesn't mention any method of specifying
start conditions. While I can see several different way of gaining
this functionality using sub-lexers and grouping, is this the most
elegant approach?

Cheers,
Julian.