{clause + after + clause after + clause, + clause}

We can use afterlo join two clauses.
We can either say: B happened after A happened

OR After A happened, B happened.
The meaning is the same: A happened first.
Note the comma (,) in the second structure.
I went to America after I left school.
After I left school, I went to America.
He did military service after he went to university.
(= He went to university first.)
After he did military service, he went to university.
(= He did military service first.)

In a clause with after, we use a present tense if the meaning is future (see 343).

I'll telephone you after I arrive. (NOT . . . after I will arrive.)

In clauses with after, we often use perfect tenses. We can use the present perfect (have + past participle) instead of the present, and the past perfect (had + past participle) instead of the past.

I'll telephone you after I've arrived
After I had left school, I went to America.

There is not usually much difference of meaning between the perfect tenses and the others in this case. Perfect tenses emphasize the idea that one thing was finished before another started.

In a formal style, we often use the structure (after + ing) .

After completing this form, return it to the Director's office.
He wrote his first book after visiting Mongolia.

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