GlobalVaribleList : Varible 
                      | GlobalVaribleList COMMA Varible

def p_GlobalVaribleList(p):
    '''
    GlobalVaribleList : Varible 
                      | GlobalVaribleList COMMA Varible
    '''
    if len(p) > 2:
        p[0] = GlobalVaribleList(p[1], p[3])
    else:
        p[0] = GlobalVaribleList(None, p[1])