Tenses Questions
The past perfect continuous tense is used to describe an ongoing action that started in the past and continued up until another point in the past. It is formed by using "had been" + present participle (-ing form of the verb).
Example: She had been studying for three hours before she took a break.
On the other hand, the future perfect continuous tense is used to describe an ongoing action that will start in the future and continue up until another point in the future. It is formed by using "will have been" + present participle (-ing form of the verb).
Example: By this time next year, I will have been working at the company for ten years.
In summary, the main difference between the past perfect continuous and future perfect continuous tenses is the time frame in which the actions occur. The past perfect continuous refers to actions that started and ended in the past, while the future perfect continuous refers to actions that will start and end in the future.