Perfect infinitives (to have + past participle) often have the same kind of meaning as perfect or past tenses.
- I am glad to have met my soul mate. (= I am glad that I have met my soul mate.)
- She was sorry to have lost her keys. (= She was sorry that she had lost her keys.)
- We hope to have reached there before sunset. (= We hope that we will have reached there before sunset.)
- You seem to have annoyed him. (= It seems that you have annoyed him.)
Perfect infinitives for unreal past
After the modal auxiliary verbs could, might, ought, should, would and needn’t, we can use perfect infinitives to talk about unreal situations.
- If you had asked, he would have helped. (You didn’t ask and he didn’t help.)
- He could have asked my permission before using my car. (He did not ask my permission.)
- She would have become a doctor if she had studied medicine. (She did not become a doctor.)
- She needn’t have sent me flowers. (She sent flowers but that wasn’t necessary.)
Note that the structure modal verb + perfect infinitive does not always refer to unreal past situations. It can also be used to indicate ideas such as probability and certainty.
- She could/ should/might / must have arrived by now.
