फ़्लैशकार्ड

The future perfect views an action from a future deadline. When you say that a delivery will have arrived by noon, noon is your future vantage point, and the delivery happens prior to that hour. The tense does not focus on when the action began. It focuses on the finished status of the action by the time the future reference point occurs.

By three o'clock, the technician will have repaired our internet router.