How do you know when to use the present perfect vs. the present perfect subjunctive?
I'm studying for my spanish final, and really need to figure the out! Please help!!! 
2 Answers
The present perfect tense is usually used for past actions that continue into the present, or continue to affect the present.
He estado dos semanas en Ecuador.
I have been in Ecuador for two weeks.
The present perfect tense is often used with the adverb "ya".
Ya han comido. They have already eaten.
Use the present perfect subjunctive when we want to express a reaction to something that has happened (already).
Siento que el gato de Juan se haya muerto.
I'm sorry that John's cat died.
Me alegro de que ella haya llegado.
I'm glad she (has) arrived.
The difference between using the present perfect indicative (he hablado) and the present perfect subjunctive (haya hablado) would be the same as with any other corresponding tenses in the two moods.
In other words, the difference would be between whether you needed the subjunctive mood or the indicative mood, and then if you need the present perfect tense or some other tense.
Once you have decided which mood is called for (are you declaring somethings or expressing a reaction to it), then you would decide on the tense.
One glaring difference between the two moods is that the subjunctive present perfect tense verb will likely be found in a subordinate clause. There is no such constraint for the indicative present perfect tense.
Criteria for the present perfect subjunctive:
The present perfect subjunctive, also known as the past or perfect subjunctive, is used when a verb or expression requiring the subjunctive in the main clause is in the present, future, or present perfect. You might notice that the same definition holds true for the regular (present) subjunctive, so what's the difference? The present subjunctive is used when the dependent clause is in the present or future, while the present perfect subjunctive is used when the dependent clause is in the past.
The Present Perfect Indicative
The present perfect tense is frequently used for past actions that continue into the present, or continue to affect the present.
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