Stand-up is in the doldrums. The best comedians have abandoned the clubs to second-raters, has-beens, and never-weres, all of whom seem stuck doing weak variations on the standards of the early 90s: dick, airline food, and Clinton jokes. In that context Rabbi Bob Alper seems a radical alternative. With his more leisurely performing style--and refusal to play to the lowest common denominator--he's a throwback to the street-smart, intensely verbal stand-ups who found their comedic voices in the 50s and early 60s in the Catskills. When Alper begins a joke with "It's tough growing up as a Jewish kid," you can almost see Rodney Dangerfield adjusting his tie or Shecky Green whirling the mike maniacally. And the punch line--"My best friend went to a church called Saint Francis de Sales. I always thought he was the patron saint of discounts"--is at once unpredictable enough to be funny and comfortingly familiar. At 53, Alper (now based in Vermont) is at least a generation too young to belong to the Alan King school of comedy, but his retro approach to stand-up seems fresh compared to the shticks of the Seinfeld-Leno-Letterman wannabes who haunt the clubs these days. Apple Tree Theatre, 595 Elm Pl., Highland Park, 847-432-4335. August 18 and 19: Saturday, 8 PM; Sunday, 2:30 PM. $22. Then at Temple Chai, 1670 Checker, Long Grove, 847-537-1771. Sunday, August 26, 7 PM. $18 in advance; $20 at the door.