Writing DSLs is very easy, and fun! The PEG grammars are very elegant to build up. I wrote a language for programmatic recipes (think scaling, unit conversion, etc) with it and it was a delight. I'd provide an example but I haven't taken the time to write a README so I haven't published it publicly yet.
Hey that's cool. Are you willing to instead share an example snippet of what the DSL itself looks like?
Here's an excerpt (which is in a map passed to peg/compile) for numeric parsing:
:nonzero-int (* (range "19") (any (range "09")))
:int (+ "0" :nonzero-int)
:decimal (cmt (* (? (<- :int)) "." (<- (some (range "09")))) ,parse-decimal)
:fraction (cmt (\* (? (\* (number :nonzero-int) :s+)) (number :nonzero-int)
"/" (number :nonzero-int)) ,parse-fraction)
:integer (cmt (number :nonzero-int) ,parse-integer)
:num (+ :decimal :fraction :integer)