Rule 1: 1. لَوْ … لَـ: the unreal condition (first look)
لَوْ if introduces a condition that did not happen, and the result clause is usually introduced by لَـ. Both verbs are in the perfect, but the meaning is if … had …, … would have …: لَوْ سَأَلْتَنِي لَعَرَفْتَ if you had asked me, you would have known. The condition is unreal: you did not ask, so you did not know. The لَـ is attached to the first word of the result, very often to كَانَ: لَكَانَ it would have been.
لَوْ سَأَلْتَ الْإِمَامَ لَعَرَفْتَ الْعَدَدَ.
law saʾalta l-imāma la-ʿarafta l-ʿadada
If you had asked the imam, you would have known the number.
لَوْ قُلْتَ لِي لَكَانَ الْعَدَدُ صَحِيحًا.
law qulta lī la-kāna l-ʿadadu ṣaḥīḥan
If you had told me, the number would have been correct.
لَوْ صَامَ مَعَنَا لَفَرِحْنَا بِهِ.
law ṣāma maʿanā la-fariḥnā bihi
If he had fasted with us, we would have been glad of him.
لَوْ عَدَّ الْحَصَى كُلَّ يَوْمٍ لَمَا خَافَ.
law ʿadda l-ḥaṣā kulla yawmin la-mā khāfa
If he had counted the pebbles every day, he would not have been afraid.
Negative result: لَمَا + perfect.