Verbs

Perfect infinitive

Perfect infinitive = (to) have + past participle

Perfect infinitives are used in the following ways:

-with a modal verb, such as must, will, would, can't, could, might and may.

• The message should have arrived yesterday.
  

-after certain verbs and be + participle/adjective (seem, look, appear, hope, be known, be thought, be said, be happy, be pleased and be sorry).

• A Queensland tiger is known to have existed.