Consider the following excerpt from Psalm 94 in the Vulgate.
Hódie, si vocem eius audiéritis, nolíte obduráre corda vestra, sicut in exacerbatióne secúndum diem tentatiónis in desérto: ubi tentavérunt me patres vestri, probavérunt et vidérunt ópera mea.
I know that an English translation of the same Psalm reads, "If today you hear his voice, harden not your hearts." At first glance, it looks to me like the present subjunctive should have been used and the translator should have written audiatis in place of audieritis.
I think audieritis is the future perfect (why isn't it audiveritis?), in which case a literal translation would be, "If today you will have heard his voice, refuse to harden your hearts." But this seems odd. Is there a certain Latin grammatical rule I'm missing? Why would the future perfect be used here? And why wouldn't it be written audiveritis?