Wildly uneven but sporadically affecting, Bobby Roth’s “Pearl” is a curiously disjointed drama that relies on the compelling performances of veteran actor Anthony LaPaglia and promising newcomer Larsen Thompson for most of its emotional impact. A few abrupt narrative transitions indicate that some scenes, for whatever reason, must have been discarded during the editing process. But what remains on screen is enough to hold attention and generate rooting interest, especially if you’re amused by inside-baseball allusions to the film and TV industry.