"De jongen zal brieven gestuurd hebben."
Translation:The boy will have sent letters.
It is used in the same way as in English
Dankjewel. I think it would be easier to understand if the sentence contained the other action happening after the future perfect action, eg, "De jongen zal brieven gestuurd hebben wanneer je aankomst" ==> Is dit goed? This would help, specially because of the lack of context. Just food for thought. BTW, how would you say the expression "JUST FOOD FOR THOUGHT" in Dutch?