G7. We use a modal (will or would) verb with have and the past participle when we are looking back from a point in time when something will have happened or looking back from the present. (Subject + Modal + Have + Past Participle) (e.g. They will have arrived by now. By the end of the decade scientists will have discovered a cure for influenza. I will phone at six o’clock. He will have got home by then. Look at the time. The match will have started. It’s half past five. Dad will have finished work.)
a. use 'would have' in past conditionals to talk about something that did not happen. (e.g. If it had been a little warmer we would have gone for a swim.)
G8. We use a modal verb with have to refer back:
a. ~ from a point of time in the past. (e.g. We were very worried. Someone might have taken the car.)
b. ~ from the present. (e.g. It is nearly eight o’clock. They will have arrived by now.)
c. ~ from the future. (e.g. We won’t eat until they arrive. They might not have had supper.)
d. or to refer to past time. (e.g. You should have helped her when she asked.)
Idiom 365
Last but not Least: more important, but not in order of mention or occurrence
Example: I would like to thank my teachers and friends, and, last but not least, my family.