The Future Perfect Tense is in fact a future tense meaning I will have done something. It is formed by using the future tense of the verb HABER (to have done something) + Past Participle.
The Past Participle is formed by removing the AR from the infinitive and adding ADO e.g.Habré hablado – I will have spoken.
The Past Participle is formed by removing the ER or IR from the infinitive and adding IDO e.g. Habré comido – I will have eaten.