The perfect progressive tense describes actions that repeated over a period of time in the past, are continuing in the present, and/or will continue in the future.
The present perfect progressive tense tells you about a continuous action that was initiated in the past and finished at some point in the past; however, the action has some relation to the present time. Use have/has + been + ing.
It has been raining, and the street is still wet.
I have been running, and I am still tired.
She has been practicing the piano, and she is much better now.
The past perfect progressive tense illustrates a continuous action in the past that was completed before another past action. Use had + been + ing.
It had been raining, and the street was still wet.
I had been running, and I was still tired.
She had been practicing the piano, and she had gotten much better.
The future perfect progressive tense indicates a continuous action that will be completed in the future. Use will + have + been + ing.
By tonight, it will have been raining several hours, and the street will be very wet.
By next summer, I will have been running for almost a year, and I will be fit and healthy.
By the time of the concert, she will have been practicing the piano for several months, and she will be much better.