Imagine a hospital ward. One doctor is holding a list of patients and talking to another doctor.
Doctor A: So which patients have you seen today?
Doctor B: I've seen him today. I've also seen her, and those two.
The action (see) took place in the recent past but is still relevant.
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The "unfinished-today" scenario is also possible.
Doctor A: So which patients have you seen so far today?
Doctor B: I've seen him today. I've also seen her, and those two.