Are you going to have finished your homework by ten o'clock?

[5jj]

I doubt that it is a reason worthy of the name, since you have not deigned to produce it.

We can manage without that attitude, thank you.

Ems's post #10 and the many British likes it received, along with your post #16, despite the fact that it didn't receive any likes, British or American.

These show that we prefer one form, not that we are prejudiced against the other.

It's perfectly fine. Just read and listen to more English. You're surrounded by the construction. It expresses nuances of meaning that the perfect construction does not.

Which rather supports my claim that it is not itself a perfect construction.

 

[Phaedrus]

Which rather supports my claim that it is not itself a perfect construction.

If all you intended by your claim that the construction is not perfect in modern English is that it is not aspectually perfective in modern English, and you did not mean to insinuate in any way that you found the construction not very good or less than fully acceptable in modern English, then I apologize for misunderstanding you and have nothing more to argue here, my argument having been predicated, I now suspect erroneously, on the assumption that you were seeking to pooh-pooh a perfectly good grammatical construction in Modern English, one which can be and often is used as an alternative to aspectually perfective constructions in modern English.