That was a bad place to go skiing – You could have broken your leg.
(那個地方不可滑雪，搞不好會摔斷腿，幸好你沒有。)? – 去滑雪了，但沒有摔斷腿
Why did you throw the bottle out of the window? Somebody could have been hurt.
(你為何要將瓶子丟出窗外？有可能到砸到人，你知不知道？) – 丟了瓶子，但沒有砸到人
I have a brilliant publisher who never went to university – he just started working when he was young and he worked hard and did very well. He would never have got that job nowadays because he would have had to have gone to a really good university and got good results to get a job here.
He may/might not have understood. (= Perhaps he didn’t understand.)
He can’t /couldn’t have understood. (= He certainly did not understand.)
Where can she have gone? She can’t have gone to school – it’s Saturday.? And she can hardly have gone to church. She may/might have gone swimming, I suppose.