Ought to have....
Well yes! I have to teach grammar too!! I tried to explain the modal perfect to one of my classes the other day... impossible thing you'll say!
This gave me an idea - Maybe I could use them to present a "situation" of "somebody's" life???
- This can't have happened to me!!
- I must have done something wrong but I didn't realize it until it was too late.
- He should have told me, but he didn't...
- I could have handled the situation differently...
Το προσκλητήριο μου έπεσε απ΄ τα χέρια - όχι δεν γίνεται - δεν είναι δυνατόν : can't have (!!!)
I should have been dead on a Sunday morning banging my head!!!
I think that after these examples nobody will forget modal perfect!!!!