According to New English File (Upper-intermediate, 2nd edition), "when you are talking about the future, use a present tense after these expressions: as soon as, until, when etc. This can be ANY present tense, e.g. present simple, present continuous, or present perfect." Then there are the following examples:
- I'll be ready as soon as I've had a shower.
- We're not going to go out until the rain has stopped.
However, no further details have been offered on whether using such different tenses would probably make any difference in the meaning of the sentences or not. My question is, what difference would it make if both present perfect tenses above were replaced by present simple?
- I'll be ready as soon as I have a shower.
- We're not going to go out until the rain stops.