Past speculation, deduction and regret

You didn’t wear your helmet? You might have had an accident! (Mogłeś mieć wypadek).

If the alarm had worked, I may have woken up on time. (Być może obudziłbym się na czas). 

You can’t come? I’ve already bought the tickets! I could have saved $50! (Mogłem zaoszczędzić 50 dolarów, ale tego nie zrobiłem, bo kupiłem bilety)

If only someone had warned us about the weather. We might not have got so wet. (Być może nie zmoklibyśmy tak, jak zmokliśmy)

Jerry isn’t here. He must have gone out. (= I’m sure he’s gone out.) 

He may have decided to go upstairs to sleep.

He could have gone to visit Michael. I know he was planning to go over to his house.

He might have gone shopping. The fridge is empty. (= It’s possible he went upstairs, but I’m not sure.)

No, he can’t have done that. Look, his wallet is here. (= I’m sure he hasn’t done that.)