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He is to have finished his work.

Does this sentence give complete meaning? And what's the meaning of (be to ) here? Can we use perfect infinitive after be to?

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It seems to mean that he is required/obliged to have finished his work by some future time. It would be clearer if that time was mentioned. E.g.:

He is to start at 9 am, and he is to have finished his work by 6 pm.

It still does not seem a tremendously likely thing to say. More often we would say it another way.