Not sure I am completely degenerating Parser.hs or providing improvement. I found a lot easier to work with these combinator

parser-snippet.hs

toParserList :: Parser a -> Parser (List a)
toParserList = bindParser (\i -> valueParser (i:.Nil))

concatParser :: Parser (List t) -> Parser (List t) -> Parser (List t)
concatParser (P p1) (P p2) = 
  P(\i -> withResultInput (\i2 a2 -> withResultInput (\i3 a3 -> Result i3 $ a2 ++ a3) $ p2 i2  ) $ p1 i)

(~~~) :: 
  Parser t 
  -> Parser t 
  -> Parser (List t)
l ~~~ r =  concatParser (toParserList l) (toParserList r) 

(~~<) :: Parser t -> Parser (List t) -> Parser (List t)
l ~~< r =  concatParser (toParserList l) r

(>~~) :: Parser (List t) -> Parser t -> Parser (List t)
l >~~ r =  concatParser l (toParserList r)

(>~<) :: Parser (List t) -> Parser (List t) -> Parser (List t)
(>~<) = concatParser

-- Example
-- /Surname: string that starts with a capital letter and is followed by 5 or more lower-case letters./
surnameParser = upper ~~< (thisMany 5 lower) >~< (list lower)