The future perfect is used to describe an action that’ll be finished or something that’ll already have happened before a certain time in the future.
Form:
– Positive sentences: subject + will + have + past participle (main verb) Example: By the time the doctor arrives, I will have taken my medications.
– Negative sentences: subject + will (+not, also shorten as won’t) + have + the past participle of the main verb (in our case = taken)
Example: By the time the doctor arrives, I will not (won’t) have taken my medications.
– Yes/no -questions: will + the subject + have + past participle?
Example: By the time the doctor arrives, will she have taken my medication? (yes/no)
– Wh- tag questions: wh-tag + will + the subject + have + past participle? Example: Why will she have taken her medications by the time the doctor arrives?