How to choose a tense for the verb "be back"?

Question

Good day!

How to choose a tense for the verb "be back"? By what rule?

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(1) He has been busy since he has been back.

(2) He has been busy since he was back.

(3) He has been busy since he got back / returned.

They say only (2) is wrong.

How come (2) & (3) have the same tenses but (2) is wrong and (3) is right?

By what rule should we understand that (1) is right and (2) is wrong?

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(4) Honey, I'm home, I'm back!

(5) Honey, I'm home, I've been back!

(6) Honey, I'm home, I've got back / 've returned!

They say only (5) is wrong.

How come (5) & (6) have the same tenses but (5) is wrong and (6) is right?

By what rule should we understand that (4) is right and (5) is wrong?

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Why should "be back" and "get back" (or more formal "return") be used with different tenses in the same situations?

Thanks!

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P.S.: "be back" is some strange verb. Maybe it belongs to some group where all such strange verbs are collected?

Answer 1

There are two questions here. One is verb choice after (temporal) since; a punctive verb usage is usually required

(so 'since he got back / returned' is idiomatic, rather than 'since he was / is back' – although in conversation "... since he's been back ..." is almost certainly acceptable nowadays).

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"I've got back" is fine though informal.

"Honey, I'm home – and I've been back!" (to an understood location) is fine. But "Honey, I'm home, I've been back!" doesn't work with the intended meaning here.

"I'm back!" (though rarely "I am back!") admittedly arguably uses the be-perfect (cf "I am returned!", now 200 years out of date), but is entirely acceptable in informal registers, and is in fact the preferred form in the UK.