The structure ‘have + past participle’ is called a perfect infinitive. Perfect infinitives can have the same kind of meaning as perfect or past tenses.
- I am glad to have found my soul mate. (= I am glad that I have found my soul mate.)
- She was sorry to have missed the show. (= She was sorry that she had missed the show.)
- I hope to have finished the job by next Monday. (= I hope that I will have finished the job by next Monday.)
- She seems to have quit the job. (= It seems that she has quit the job.)
Unreal past situations
The perfect infinitive is often used after verbs like mean, be, would like etc., to talk about unreal past situations.
- She was to have returned yesterday, but she fell ill.
- I meant to have posted the letter, but I forgot. (I did not post the letter.)
The perfect infinitive is also used after the modal verbs could, might, ought, should, would and needn’t to refer to unreal situations.
- You should have telephoned – I was getting worried. (The person didn’t phone.)
- She needn’t have come. (She came.)
- I would have gone on a vacation if I had had more money. (I didn’t go.)
Note that the structure modal verb + perfect infinitive does not always refer to unreal past conditions. It can also be used to express certainty or possibility.
- She should have arrived by now. (=It is possible that she has arrived by now.)