"Get off my premises before I call the police," the farmer told the boys.

Is 'before' correctly used in the sentence? I feel it should be 'or' OR 'or else'.

Thanking in advance.
That's a very common way to say something.

Knock it off before you really piss me off.

I'd better go before I get myself in trouble.

(If you don't leave, I'll call the police; If you don't knock it off, I'll get really pissed off; If I don't go, I'll myself in trouble.)
Go away before I call the police.

Go away or (else) I'll call the police.
Neither of these would be found in a passage written in formal English. At least I can't imagine an essay, news article, or scientific paper that would contain the idea of threatening to call the police -- unless it was quoted, of course.
Both expressions are in the same neutral register, however. Neither is particularly more or less formal than the other.
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Thanks, GG.

Is 'or' OR 'or else' the better choice in place of 'before'?

Thanks again.
Or I will... is fine.
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Sorry to ask the same question again.

Go away before I call the police.

Go away or else I call the police.

I wanted to know whether 'or esle' is better than 'before' in formal English. Sorry for being not clearer earlier.
 CalifJim's reply was promoted to an answer.