Present Tense/Present Perfect Tense

[blissful]

Hi

I understand that we can use the present tense or present perfect tense in these sentences.
What are the differences in meanings when using present perfect tense or present tense in these sentences?

1) I’ll come home after I do (or have done) the shopping.
2) I’ll get the dinner ready when I finish (or have finished) reading this book.

[5jj]

There is very little difference in meaning in those two examples. The present perfect lays emphasis on the completedness of the action,, but this is suggested by 'after' anyway.