'I have eaten' is the present perfect tense of the verb 'to eat', 'I had eaten' is the past perfect and 'I will have eaten' is the future perfect.

I have eaten是动词eat的现在完成时；I had eaten是过去完成时；I will have eaten是将来完成时。

《牛津词典》

We use the future perfect tense to talk about an action that will be completed at a given time in the future.

我们用将来完成时态来形容一个在未来特定的一个时间已经完成的动作。

youdao

We use the future perfect continuous tense to talk about how long an action will be going on at a future time.

我们用将来完成进行时态来形容一个行动在未来特定的时间里已进行多久了。

youdao

Not only is it not too late to save for the future, it may be the perfect moment to begin.

FORBES: Gen-Xers, Millennials May Reap Big Benefits From Great Recession

And as to number fudging, there are ways to provide the public with an independent cross-check but there is no perfect predictor of the future.

FORBES: Why Does Everyone Want A Train Set And Not Everyone Wants To Build A Train?

I've talked to Russian analysts who say if you think about this five, ten, fifteen years into the future, they fear that the United States will perfect this technology - it's unperfected so far - and put more missile interceptors either in eastern Europe, Poland or on ships not far from Russia, and that ultimately - the Russians say - they fear that this could challenge their nuclear deterrent.

NPR: U.S., Poland Sign Missile Defense Deal