1: We use modals plus the present perfect to speculate an alternative outcome to a completed action.
- I should have studied more in school.
- We should have saved some money.
- I would have been upset.
- I could have been a contender.
2: We use the third conditional to express an outcome we cannot change.
- If I were you, I would have said something.
- If I could do it over, I would have changed jobs.
- If we had won, I wold have been happy.
- If the weather had been nicer, we would have stayed longer.
3: We use wish + past perfect or wish + would + present perfect to show regret. The meaning is the same.
- I wish I had tried harder in school.
- I wish I would have tried harder in school.
- She wishes she had applied for the job.
- She wishes she would have appled for the job.
4: The modal changes the meaning of the word.
- I would have said something. (I did not have the chance)
- I could have said something. (I had a chance, but did not)
- I should have said something. (I regret not saying something)
- I must have said something. (I speculate I said something)
- I might have said something. (The outcome might differ)
- I may have said something.