· is used to express actions in ‘if clauses that did not take place:
If you had listened to me, you could’ve avoided mistakes.
(=You didn’t listen to me and so you couldn’t avoid making mistakes.)
If you’d explained your problem to your boss, he’d have understood it.
(=you didn’t explain your problem to your boss and so he didn’t understand it.)
If she hadn’t married him, she’d be living now.
(=She married him and now she is no more.)
· expresses unrealized hope or wish:
I had hoped we would be able to leave tomorrow but I have an emergency operation.
I had intended to see my mother but I have to stay back and finish my report.
I wish I had taken your advice. [ But I did not]
We had expected you to stay at least a week [But you are not]
Past Perfect Progressive
1. duration of past actions:
It was getting dark and he was exhausted because he had been digging since
2. repeated past actions:
He had been trying to get on the phone, but he was unsuccessful.
3. duration of actions earlier than the completed ones:
When I opened the door I found him on his knees outside. I knew
he had been looking through the keyhole.