When do we use present perfect subjunctive?

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I don't think it exists in English. It is a Romance-language verb form.
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Here's an example:

"The court is not precluded from deciding this issue, even though the plaintiff did not address it in his appellate brief. The statute requires only that the plaintiff have had the opportunity to address the issue."

It seems to me that the present perfect subjunctive is used to refer to the past when the present subjunctive is used to refer to the future. In your sentence the subjunctive is due to requires.I don't think many grammarians recognize this verb form, though. I have never heard of it. That doesn't mean I consider it wrong. The few grammatical forms that English has are used in amazingly col

heloOOhow is present perfect subjunctive used in English?

Very carefully! And very sparingly!

Provided the semantics allow it, the syntax is the same as for the present subjunctive of have, plus the past participle. The present subjunctive, if not the present indicative, usually substitutes, as the subjunctive form sounds too "fussy" to many