how to use "present perfect" ?

[endeavor6636]

as the title shown how to use present perfect>?

[Mister Micawber]

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It has several uses, but as I said in answer to your other post, use it when a past event relates to the present time in some way:

I've lost my key. (at some time between the past and right now, and do not know how to get into my house)
I have never seen a purple cow. (from the past until now)
I have always eaten sushi on Sunday. (from the past until now and I intend to continue into the future)
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