Mr. Birbiglia - who came to national attention with the stage and film versions of 'Sleepwalk With Me,' an autobiographical account of his dangerous nights with a sleep disorder - seems not only to occupy but also to absorb and transmute every inch of the Cort's naked stage. (Appropriately, there's more to Beowulf Boritt's bare set than first meets the eye.) He achieves this partly by pacing, pacing as he talks, in ever-widening circles and diagonals and loop-de-loops.