f.rb

Eur = Struct.new(:euro, :cents)

euroParser =

    # Lets first parse some digits
    digits >
        -> eur {
            # Then parse a comma
            char(',') >>
                # Then parse some more digits
                digits >
                    -> cents {
                        # Then an optional comma
                        maybe(char('€')) >>
                            # If everything has parsed, we can produce a new result.
                            pure Eur.new(eur, cents)
                    }
        }