have:

verb

和一个过去分词用于形成现在完成时,过去完成时,将来完成时,和条件语气。

be for...or是一个过时的结构,交换动词和主语,使用动词的虚拟语气形式,表达一个条件句。

它更多存在于过去(除了were,虚拟语气和普通的过去式一样)。所以:

Had I known ... = If I had known ...

Had he seen it, ... = If he had seen it, ...

Should you want me, ... = If you should want me, ... = If you wanted me, ...

Were I to say that, ... = If I were to say that, ... = If I said that, ...

这些过去式有些书面,但偶尔会在演讲中使用。

下面的现在时更加书面,很少使用除了故意:

Be he good or evil, ... = Whether he is good or evil, ...

Be it so or not, ... = Whether it is so or not, ...