Abu’l-Qāsem Khān Qarāgozlu ( Persian : ابوالقاسم‌خان قراقزلو ), known by the title Nāṣer-al-molk ( Persian : ناصرالملک , lit. ' Assistant of the Realm ' ), (July 13, 1856 – 26 December 1927) was an Iranian politician who served as Regent , Prime and Finance Minister of Iran during the Qajar dynasty .