Bishop Pirih was born into a Roman Catholic family of Mirko and Štefanija (née Šuligoj) in the present day City Municipality of Nova Gorica,[2] that in this time was governed by Italians and was baptized at the local church on the day of his birth.

Pirih served a short time as a parish priest in Solkan (1963–1964) and after that became a personal assistant to Bishop Janez Jenko from 1964 until 1974, when he continued his postgraduate studies at the Pontifical Theological Faculty Teresianum in Rome, Italy with a master's degree in the camp of a spiritual theology in 1976.

After returning to his homeland, he became a spiritual director at the Major Theological Seminary in Ljubljana (1976–1984), and in 1977 he again became Bishop Jenko's personal assistant.

As an educator of future priests, he remained in Ljubljana until 1984, when Bishop Jenko appointed him a Vicar General of the Diocese of Koper.

[2] On March 25, 1985, he was appointed by Pope John Paul II as the Coadjutor Bishop of the Roman Catholic Diocese of Koper.