I have a grammar exercise which is: "Time Clauses Referring to the Future. Compare the sentences, how does the meaning change when the Present Perfect is used?"
- Come over and see us when our guests leave.
- Come over and see us when our guest have left.
- We can go out as soon as we have had dinner.
- *We can go out as soon as we have dinner.
I would like to ask you what does it mean when the Present Perfect is used and what does it mean when Present Simple is used? Also it is confused to me what "*" mean in the sentence 4, because it is not explained.