1- There are times when we want to talk about consequences of a future action. Here, the verb that is the condition of the sentence comes in the present subjunctive tense. However, one might find this odd since its name suggests that it should talk about present actions.
اگر محسن بیاید، من هم میآیم.
If Mohsen comes, I’ll come too.
2- Suppose an action could happen in the past but it did not, now we are talking about the result it could have if it had happened.
اگر حقیقت را میگفتم علی میمرد.
اگر حقیقت را گفتهبودم علی مرده بود.
If I told the truth, Ali would die.
If I had told the truth, Ali would have died.
As you see, the verbs in such sentences come either both in past imperfective tense or both in past subjunctive tense. One should note, however, that it is common in today’s Persian to use either of these two tenses in any of the positions, at times conveying slightly different meanings.