Student or Learner
I'd like to know the difference between "1" and "2"
1. He should be here by now.
2. He should have been here by now.
#2 can have another meaning that #1 can't have. This meaning is that he was suppossed to come here, maybe to see something or to check something, but he didn't need to stay here after he did what he came to do. In other words, he probably was here but then left.