Perfect Tense

The conjuction of the verb "to have" determines the tense of the overall construction :
1.Have and Has in the present perfect tense

•   The girl has eaten the cookie

2.Had in the past perfect tense

• The girl had eaten the cookie before she ate her lunch

3.Will Have and Shall Have in the future perfect tense

• The girl will have eaten the cookie by this afternoon

Present Perfect Tense
The present perfect tense is formed with the subjectplus the correct form of the assist verb 'have' plus the past participle (the third form) of the principal verb. The present perfect tense can be used in positive, negative and interrogative.
The pattern :
Positif : S + have / has + V3

• She has broken my heart

Negative : S + haven't / hasn't + V3

• We haven't spent your money

Interrogative : Have / Has + S + V3 + ?

• Has he drunk jus ?

We use the present perfect tense to say that an action happened at an unspecified time before now. The exact time is not important. You can't use the present perfect tense with specific time expression such as : yesterday, one year ago, last week, etc. But we can use the present perfect tense with unspecific such as : ever, never, since, for, just, already, yet, once, many times, several times, before, so far,etc.
Example :

• Have you read the book yet ?
• I have followed this extracurricular since junior high school

Past Perfect Tense
Past perfect tense is a kind of tense that is used to describe an action or an event that started in a certain time in the past and completed or finished till certain time in the past too. Past perfect tense is used to express an action or an event that had happened before the other event or action happened.
Example :

• When I arrived, the plane had left
• Before I went to Canada, I hadn't been abroad

The pattern :
Positif : S + had + V3 + Complement

• He had eaten

Negative : S + had + not + V3 + Complement

• He had not eaten

Interrogative : Had + S + V3 + Complement

• Had he eaten ?

Usefulness
Past perfect tense is used to refer to an event or situation which took place before another past event. There are some rules that need to be considered and the following are some examples to help you see how it is used.
Examples:

• I wasn't busy yesterday because I had already finished my work
• When I arrived, the concert had just started

Future Perfect Tense
Future perfect tense is used to indicate the time of the completion of something. The future perfect tense is quite an easy tense to understand and use. The future perfect tense talks about the past in the future. Future perfect tense has to different forms : "will have done" and "be going to have done". In speaking with the future perfect tense, we often contract the subject and will. We sometimes use shall instead of will, especially for I and we.
The pattern :
Pasitive : S + will + have +V3

• He will have gone to America by the end of the month

Negative : S + will + not + have + V3

• He won't have gone to America until next month

Interrogative : Will + S + have + V3 +  ?

• Wiil he have gone to America by the next month ?