1. The Future Perfect denotes an action completed before a definite moment in the future.
I shall be back by six, and I hope you will have had a good sleep by that time.
(Marryat)
2. The Future Perfect can denote an action which will begin before a definite moment in the future, will continue up to that moment and will be going on at that moment. This use of the Future Perfect is called the Future Perfect Inclusive.
The Future Perfect Inclusive is used with verbs not admitting of the Continuous form, in negative sentences, with non-terminative verbs such as to work, to live, to study, to teach etc.
I shall have been a teacher for 20 years by next May.
I shall have worked as a teacher for 20 years by next May.
THE FUTURE PERFECT IN THE PAST
The formation of the Future Perfect in the Past.
1. The Future Perfect in the Past is formed by means of the Future Indefinite in the Past of the auxiliary verb to have and Participle II of the notional verb.
2. In the interrogative form the first auxiliary verb is placed before the subject.
In the negative form the negative particle not is placed after the first auxiliary verb.
Affirmative
Interrogative
I should have worked
He would have worked
She would have worked
We should have worked
You would have worked
They would have worked
Should I have worked?
Would he have worked?
Would she have worked?
Should we have worked?
Would you have worked?
Would they have worked?
Negative
I should not have worked
He would not have worked
She would not have worked
We should not have worked
You would not have worked
They would not have worked
3. The contracted affirmative forms, are:
I’d have worked
He’d have worked
The contracted negative forms are:
I shouldn’t have worked
He wouldn’t have worked
4. The negative-interrogative forms are:
{Should I not have worked?
Shouldn’t I have worked?
{Would he not have worked?
Wouldn’t he have worked?
The use of the Future Perfect in the Past.
The Future Perfect in the Past is used to denote an action completed before a definite moment which was future from the point of view of the past.
I wondered whether they would have reached the place by noon.
(For detailed treatment see Chapter XVIII.)
THE PERFECT CONTINUOUS FORM
The Perfect Continuous form denotes an action in progress, whose duration before a definite moment in the present, past or future is expressed.
It is formed by means of the auxiliary verb to be in one of the perfect tenses and Participle I of the notional verb.