It might be good to note, that "Have you had it?" can also be used as past tense.

Cereal Nommer‭ I'm not sure what you mean by that.

Moshi‭

Present perfect tense - A: "I have a headache." B: "How long have you had it?"

Referring to a currently ongoing headache.

Past tense - A: "You should try the soup." B: "Have you had it?"

Referring to a possible previous instance of soup eating.

Cereal Nommer‭ Isn't that just the normal usage of the present perfect, and not especially unique to 'have'? Or am I misunderstanding something. We can do the same for say, 'eat', e.g. "Have you eaten it?"

Moshi‭ Not especially, but the usage of "have" is often pretty important to determine tense. "Have you eaten it?" would only be present perfect tense when referring to the experience of having eaten something. More often it would have the same meaning as "Did you eat it?" which is unambiguously simple past tense.

Even looking back on my previous comment, I can see that B: "Have you had it?" is ambiguous as to tense. "Have you had it before?" would be more clear. Though it's rarely that important to clarify intent that precisely.

"Have you eaten it?" would only be present perfect tense when referring to the experience of having eaten something

Cereal Nommer‭ "Have you eaten it?" is present perfect tense, because that is the grammatical category it falls into. While I don't disagree that it can sometimes be used interchangeably with the simple past, it would be wrong to say that that usage is not present perfect.

In any case, the point of this answer wasn't to explain what the present perfect is, but simply to show how to form it with the verb 'have'; I assume that OP is aware of the usage of the construction.

Moshi‭ Fair enough. I feel like there's enough English language learners who might read this in the future that it's worth noting that depending on context there could be some ambiguity. If you told me casually "The police arrested an escaped murderer." I would want clarification whether you meant, "The police have arrested the murderer, who escaped earlier." or "The police arrested a murderer, who has escaped."