matcharglist : matcharg
                 | matcharglist COMMA matcharg

def p_matcharglist(p):
    '''
    matcharglist : matcharg
                 | matcharglist COMMA matcharg
    '''
    if len(p) == 2:
        p[0] = [p[1]]

    else:
        p[0] = p[1]
        p[0].append(p[3])