Sorry, this is a bit off-topic but I post here because:

* it is about a DSL and many Haskellers are fond of DSLs,

* the first implementation is written in Haskell.

http://www.cosmogol.fr/

describes a proposal to the IETF to standardize the language used for
finite state machines (which are common in IETF standards), much like
ABNF is standardized in RFC 4234, to describe grammars.

The reference implementation, available at
http://www.cosmogol.fr/shadok.html is in Haskell.

Bug reports, patches, advices, flames, opinions and criticisms are
welcome.