What is the meaning of 'past perfect progressive tense'?

Answer 1

English does not have any formal past perfect progressive tense, and I doubt that any other language has any such tense, because in English the past perfect tense expresses the fact (or at least belief) that the action or linkage indicated in the basic meaning of the verb occurred and was complete at some time in the past. Example: "By the year 2000, the population of the United States had exceeded 300 million people", where the italicized words are the past perfect tense of "exceed". In contrast, an English progressive tense expresses the idea of continuing action or linkage, which is logically incompatible with the meaning of a past perfect tense. If a foreign language does have a formal past perfect progressive tense, it may be possible to translate such a verb into English by using a present perfect conditional tense, as suggested by one earlier contributor with the example "I would have been walking home from school."

Answer 2

The past perfect progressive tense is used to describe an action that was ongoing in the past, was interrupted by another action, or continued for a period of time. It is formed by using had been + present participle of the verb (e.g., had been studying).