Perfect infinitives can have the same meaning as perfect tenses or past tenses.
- It is nice to have heard from her. (= It is nice that I have heard from her.)
- I’m glad to have won. (= I am glad that I have won.)
- She is glad to have represented her country in the Olympics. (= She is glad that she has represented her country in the Olympics.)
- I am glad to have left school. (= I am glad that I have left school.)
The perfect infinitive is often used to talk about unreal past events.
- I meant to have posted the letter, but I forgot.
Perfect infinitives are quite common after modal auxiliary verbs like would, should and could. Note that after a modal auxiliary verb, the perfect infinitive is used without to.
- You should have asked me before borrowing my car.
- She should have consulted a doctor.
- They should have told us they weren’t coming.
- I could have married anybody I wanted.
Perfect infinitives in third conditional sentences
Third conditional forms are used to talk about unreal past situations. Here we use a past perfect tense in the if-clause and would + perfect infinitive (have + past participle) in the result clause.
- If I had worked harder, I would have passed the test.
- If she had applied in time, she would have got the job.
Note that the structure modal verb + perfect infinitive does not always refer to unreal past situations. It can also be used to express our belief that something has happened.
- 6 o’clock. She should have reached home now.
