1. She might be having lunch.
2. I shouldn't have eaten so much.
3. He must have forgotten.
4. You needn't have gone home so early.
5. It can't be changed now.
6. She ay be watching television.
7. She must have been waiting for somebody.
8. he couldn't have done it.
9. You ought to have been here earlier.
10. I would have helped you.
11. You should have been warned.
12. He might not have been feeling very well. / He might not have felt very well.