def p_raw_list(t):
    """raw_list : expression COMMA expression
                | raw_list COMMA expression
                | raw_list COMMA raw_list
    """
    if type(t[1]) is list:
        t[1].append(t[3])
        t[0] = t[1]
    elif type(t[3]) is list:
        t[3].insert(0, t[1])
        t[0] = t[3]
    else:
        t[0] = [t[1], t[3]]
