A 形式

to have been+现在分词：

He seems to have been spying for both sides．

他似乎一直在为两方面搞秘密情报。

B 用法

主要用于助动词之后和appear，seem之后，但也可以用在happen， pretend以及believe， know， report， say， understand的被动式之后：

—He says he was talking to Tom．

—He couldn’t have been talking to Tom．Tom wasn’t there．

—他说他当时在跟汤姆说话。

—他当时不可能在和汤姆说话。汤姆当时不在那里。

—I was following Peter closely．

—You shouldn’t have been following him closely；you should have left a good space between the two cars．

—当时我正紧紧地跟着彼得。

—你不应该紧跟着他；而应该使两车之间保持相当的距离。

He appears to have been waiting a long time．相当于：

It appears that he has been waiting a long time．

看来他已经等了很久了。

He pretended to have been studying．相当于：

He pretended that he had been studying．

他假装一直在学习的样子。