Oxford Modern English Grammar underscores the relevance of the action/state in the present perfect to the present point of reference (the moment when you speak of it), which I take as that that action/state is still relevant/important and/or still has effects / impacts / desired/expected (be it implicit or explicit) results on the very current situation.
- I have finished the work that I had to do. (I can now take on new work.)
- I have been unwell for the past 6 weeks. (I haven't been productive as an aftereffect.)
Compare the past simple in which the action/state has no relevance to the present moment (over and done with).
- I was unwell last week. (I'm totally okay now.)
The book lists such uses of the present perfect as continuative (leading up from the past to the present - thus still somewhat relevant), of the recent past (recent - thus relevant), of result (having identifiable results now - thus relevant). The last use is experiential.
- I have toured the Voronezh.
- Well, these damn plants have shot up in price so much over the last year or two.
- Have you seen it before , Caroline?
- Have you ever seen ‘Married with Children’?
The latter three examples can be categorized as continuative as they denote the fact that the "shooting up" and the "seeing" are arguably considered from a present reference point and still relevant at the moment of speaking. But the first example confuses me. In what way would the "touring" be relevant to the present moment? I've also heard similar experiential examples such as "I've been to Canada", "I've been there twice". Shouldn't such experiences be over and done with as they don't really have conceivable effects on the present and may not be recent at all, and therefore be in the past simple?
All examples noted here are from the book.