At the trial of his fellow student, Robert Emmet, in 1803, when the sentence of death was pronounced, Perrin rushed forward in the court and warmly embraced the prisoner.
Being unseated in August, he was returned to the House of Commons for Monaghan at the general election on 24 December 1832, displacing Henry Robert Westenra, the previous Tory member.
He was most painstaking in the discharge of his important functions; and, despite some peculiarities of manner, may be regarded as one of the ablest and upright judges who have sat on the Irish bench.
He resigned on a pension in February 1860, and resided at Knockdromin near Rush, County Dublin, where he frequently attended the petty sessions.
Abraham Augustus Stewart, chaplain to the Royal Hibernian School, Dublin and his wife Frances Connor of County Donegal, by whom he had seven sons, including James, a major in the army, who fell at Lucknow in 1857; Louis, rector of Garrycloyne, Blarney, County Cork; William, chief registrar of the Irish Court of Bankruptcy (d 1892); Charles, major of the 66th foot from 1865; Mark, registrar of judgments in Ireland; and John, of Fortfield House, Terenure, father of the well-known painter Mary Perrin.