Consider these two examples,
- I will have had eaten by that time.
- I will have had been working there for five years.
To me, the first sentence seems to express the proposition that, it is the present (t1); I will begin eating in a future moment (t2); finish eating by sometime after that (t3); and that eating will be relevant to the time referenced in the sentence, "that time" (t4).
Whereas, to me the second sentence seems to express the proposition that, it is t1; I will begin working somewhere at t2; I will continue working there until t3, at which time I will stop working there; and my time working there will be relevant to a later time that the speaker is discussing, t4.
Are these configurations grammatical? Do they have names?