Sometimes my brain can surprise me. Today it remembered that a sentence of the type "If I had known, I would have..." construction in Spanish uses the pluperfect subjunctive. (OK, I wasn't perfect, I thought the first clause should be in the simple past perfect.) (I googled because I was curious. By the way, there was a reason for me thinking of this.)
Ah ha, the result clause may be in either the imperfect subjunctive or the conditional perfect; the latter makes more sense to me. Thinking about it, I should have known that the first was subjunctive: counterfactual if-clauses ("If I had known [which I didn't]") are in the subjunctive in Spanish.
I last studied Spanish about 7 years ago so I'm amazed I remembered that. I was never fluent either (I still can't conjugate verbs in vosotros [2nd person plural familiar] because they skipped it at school [many dialects omit it]). Although I did always have a pretty good grasp of verb tenses, which is good, because Spanish has plenty of them and unlike French, none other than the future subjunctive has dropped out of use. (Although this is useful in its own way because tense correspondence is somewhat closer to English.)
Yes, I am a multilingual grammar whore.