what is the The present perfect subjunctive used for?
what is the The present perfect subjunctive used for?
2 Answers
This might give you a bit of insight. 
The present perfect subjunctive
Exactly the same as the present perfect indicative, but in subjunctive. Easy!
Whatever book you are using is probably deceiving you. Present perfect subjunctive is, like any subjunctive, a virtual idea, and being a present perfect, is an affirmation that has a certain connection with the present moment.
Espero que te hayas diverdido = I hope you've had fun.
It is a virtual idea, since you can't tell whether the person has had fun, and it is a perfect tense because it has (virtually) happened, and it is related to the present moment.
In short: to give a virtual (subjunctive) affirmation (present) that has some relevance now (perfect).
