Learning to Use the Future Perfect Tense
The Future Perfect can be best visualised as a two-step concept. The first step is to go to an imagined point in the future. From there you go backwards to see what happened in the period leading up to this future time.
The Core Characteristic of the Future Perfect is to describe an imagined past of a future time. By a certain point in the future, the speaker predicts what the past will look like:
|I will have finished eating by the time the movie starts|
In this sentence, the first step Reference Point (R) Step 1, is to conceptualize the time when the movie starts. From here you move back in time to Reference Point (R) Step 2. This is the undefined time in which you will have finished eating your ice-cream.