Present PerfectShe has written an e-mail
Has she written an e-mail?
What has she written?
Has she written an e-mail or letter?
She has written an e-mail, hasn't she?
Past Perfect
They had eaten all food before he came.
Had they eaten all food before he came?
What had they done?
Had they eaten all food or drunk everything before he came?
They had eaten all food before he came, hadn't they?
Future Perfect
I will have read a book by 4 tomorrow
Will I have read a book by 4 tomorrow?
What will I have done by 4 tomorrow?
Will I have read a book by 4 or by 6 tomorrow?
I will have read a book by 4 tomorrow, won't I?