       ident = Word(alphas, alphanums)
            num = Word(nums)
            func = Forward()
            term = ident | num | Group('(' + func + ')')
            func <<= ident + Group(Optional(delimited_list(term)))
            result = func.parse_string("fna a,b,(fnb c,d,200),100")
            result.pprint(width=40)

        prints::

            ['fna',
             ['a',
              'b',
              ['(', 'fnb', ['c', 'd', '200'], ')'],
              '100']]
        N)