INFINITIVE WITH “TO”
A perfect infinitive is an infinitive in the form of “to have + past participle”. It is used after some verbs to emphasize that something happened in the past.
She seems to be very optimistic.
She seems to have been very optimistic.
She seemed to have been very optimistic.
He pretended not to have noticed me.
I happened to have seen that film before.
I’d like to have met him.
Perfect infinitive also appears in the passive voice:
He is supposed to have met the American president.
Mia is considered to have been the best manager of the company.
Perfect infinitive continuous is an infinitive in the form of “to have been + verb + ing”. It is used after some verbs to emphasize that something happened in a particular moment in the past.
He seems to have waited for a long time.
When I saw him, he seemed to have been waiting for somebody.
Other examples both in the active and passive voice:
She pretended to have been reading, but in fact, she was listening to their conversation.
He is reported to have been talking to a spy.
INFINITIVE WITHOUT “TO”
Structures “would rather” and “had better” require the use of infinitive without “to” as well.
|would rather|| I’d rather spend the night at home than go to a party.
We’d rather wait till tomorrow.
|had better||You’d better stop talking about that, or else.|
Perfect infinitive stands after auxiliary verbs to express unnecessary actions, not fulfilled wishes and duties, missed or belonged do the past chances, make guesses about something that’s passed etc.
We shouldn’t have bought that camera. It was a waste of money.
He could have been killed.
She may have left.
It’s closed. They must have finished work earlier today.
A passive gerund is nothing but a verb with -ing ending in the passive voice. It may appear in one of two forms: present (e.g. being shown) and past (e.g. having been shown).
The passive gerund in present
I remember being taken to the hospital.
I hate being spoken to as if I’m a child.
The passive gerund in past
He showed no signs of having been warned.
The notice, having been written in small letters, was not clearly visible.