I have heard that pluperfect is simply past tense relative to a subsequent past moment rather than to the moment of the utterance. “I had blown out the candle” indicates that this event occurred prior to some past event.
I have heard that future perfect can also be analyzed as relative to some prior future event. “I will have done my homework” indicates that the completion of my homework occurred in the future but before some other future event.
Is present perfect always relative to the moment of the utterance? I’m not sure, because some present events are ongoing. “He has climbed Mt. Everest” indicates an event that was completed before the moment of the utterance.
I know that different linguistic theories analyze linguistic data differently, and that some analyses are more useful in some contexts than in others.