What is the Future Perfect Tense?
pattern = will + have + past participle
Future perfect - is used to show something that will happen before a future event happens or takes place.
I will have eaten my pizza by lunch.
By next week, she will have given birth.
Using the word by gives the future event, by next week, by next year, by tomorrow, are all events/times in the future.
We use the future perfect to show something that will happen by that time.