Основы теории английского языка. Листунова Е.И. - 54 стр.

       In Russian this form of the infinitive is often rendered by a finite
form of the verb:
       ß î÷åíü ðàä, ÷òî ïîâèäàë âàñ îïÿòü. Ìíå æàëü, ÷òî ÿ òàê
ìàëî ïîìîã âàì.
       When a perfect infinitive is associated with a modal (defective)
verb the infinitive indicates:
       1) Either that the action took place in the past; then the in-
finitive is equivalent to a past:
       Why did she go away so early last night? She may have been ill
(perhaps she was ill). You must have been very tired if you went to bed
so early (probably you were very tired...).
       2) Or the infinitive indicates that the action is already accom-
plished at a given moment and is viewed from that moment; then it
has the meaning of a perfect (present perfect or past perfect):
       Why doesn’t she come? She may not have arrived yet (perhaps she
has not yet arrived). Let us go, it must have stopped raining (probably it
has stopped raining). She may have gone before they arrived (perhaps she
had gone before they arrived). He must have locked the door before he
left the house (certainly he had locked the door before he left the house).
       The perfect continuous form of the infinitive shows the anterior
duration of an action still continuing; it is equivalent to a present or
past perfect continuous:
       We must have been walking for two hours; let us have a rest
(probably we have been walking for two hours...) For a quarter of an
hour I must have been writing by a glow of firelight reflected on to my
desk (probably I had been writing...); it seemed to me the sun of
summer (Gissing).
       After the modal (defective) verbs should, could, ought, might
(subjunctive II) and the past indicative of the verb to be (when used as
a modal equivalent) the perfect infinitive is used to show that an action
considered desirable or planned was not carried out (a rejected action):
       You should have phoned me at once... (Gordon). I ought to have
done it (Locke). The yellow leaves came down about those two walking
the mile and a half which Soames had traversed so often in those
long-ago days when he came down to watch with secret pride the
building of the house which was to have been the home of him and
her from whom he was now going to seek release (Galsworthy).
       After the past tense of verbs expressing hope, expectation, intention,
the perfect infinitive is used to indicate that the action was not carried out:

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