When a character in a play so shreds your nerves that you find yourself itching to throttle him within the first 15 minutes, you can be sure an exhilarating night at the theater is not on the menu. When said character is one of only two in the play, the sole item on the menu is likely to be unrelieved agony. This, unfortunately, sums up my experience at John McManus’s comedy “The Quare Land,” which opened on Thursday at the DR2 Theater in an Irish Repertory Theater production. Despite two excellent performances – from Peter Maloney as that irritant and Rufus Collins as the play’s more palatable but far less loquacious character – the play grinds on for 90 minutes, sustained by what is essentially a single joke. Mr. Maloney portrays Hugh Pugh, a 90-year-old Irishman who lives on a much-neglected farm, home to just nine cows despite its dozens of acres. He’s in the bathtub as the play opens. (Spoiler alert: He never gets out of it.) Hugh is having his first soak in 48 months, he cheerfully announces, when Rob McNulty (Mr. Collins), a building developer who’s been trying to contact him for some time, knocks on the door and is welcomed into the bathroom for a chat.