The perfect continuous indicates a continuous action that has been finished at some point in the past or that was initiated in the past and continues to happen. The action is usually of limited duration and has some current relevance:
The perfect continuous uses the verb have or has.
Present Perfect Continuous
The present perfect continuous is used with actions that began in the past and are still continuing.
It’s made with the present tense of have + been + present participle (root + ‑ing). You’ll most often see this verb tense used with the words for and since.
Past Perfect Continuous
The past perfect continuous is used when one activity in the past was happening before or after another activity had taken place.
The past perfect continuous is written by using the past tense of have + been + present participle. Look for the words for, since, and before.
Future Perfect Continuous
The future perfect continuous tense is used much like the future perfect, but one of the actions is likely to continue beyond the other. It can also be used when one action will be continuing at a certain time in the future.
Create the future perfect continuous this way: will + have + been + present participle (root + ‑ing). Look for key words like in and by.