escapeHex :: Parser ByteString
escapeHex = fmap fst $ match $ do
  char '\\'
  satisfy $ inClass "xX"
  satisfy $ inClass "A-Fa-f0-9"
  Parser.option () $ satisfy (inClass "A-Fa-f0-9") *> pure ()
escapeHex :: Parser ByteString
escapeHex = fmap fst $ match $ do
  char '\\'
  satisfy $ inClass "xX"
  satisfy $ inClass "A-Fa-f0-9"
  Parser.option () $ satisfy (inClass "A-Fa-f0-9") *> pure ()
escapeHex = fmap fst $ match $ do
  char '\\'
  satisfy $ inClass "xX"
  satisfy $ inClass "A-Fa-f0-9"
  Parser.option () $ satisfy (inClass "A-Fa-f0-9") *> pure ()