(By Östen Dahl and Viveka Velupillai): "By perfect we mean a category with approximately the same semantics as the English (Present) Perfect in I have read this book, which is used to express events that took place before the temporal reference point but which have an effect on or are in some way still relevant at that point. This includes at least two related but distinguishable uses: (i) A perfect may be used resultatively, i.e. of an event, often but not always a recent one, which has results that hold at the time of speech (or any other time serving as reference point): Someone has stolen my purse! (=the purse is gone). (ii) A perfect may be used experientially, i.e. to say that a certain type of event took place one or more times over an interval of time, typically one that extends up to the moment of speech (or whatever time serves as the reference point): I have seen worse things in my life. ❡
Constructions that have only one of these two uses (dedicated resultatives and experientials) have not been treated as perfects here. Admittedly, the information given in grammars is not always specific enough to make reliable decisions on this point."