rated R

To get a good idea of what to expect from the new break-up comedy “Forgetting Sarah Marshall,” look no further than it’s star and writer, Jason Segel. A veteran of Judd Apatow’s televised “Freaks and Geeks” school, with a brief stint on “CSI,” you may have last noticed him as Seth Rogan’s towering slacker friend in “Knocked Up.” Like many of the men on Apatow’s crew, he comes across as a doughy, needy, ne’er do well, with a sly comic outlook and an undeniable attraction to smokin’-hot ladies. This movie is a lot like that.

In writing the film (which Segel admits is 80 percent autobiographical—including having worked on a musical production of “Dracula” written for puppets and having once been mercilessly dumped by a girl while completely naked), he’s put himself completely on the line. There’s a clear and heartfelt sincerity to all the characters, like ’em or not, which connects the audience to their plights and buoys the comedy in a way few other film producers have even attempted.

In fact, beyond the excruciating hilarity of seeing Segel’s poor, discarded schlub of a character drop his towel in shock as his successful, actress girlfriend drops the axe, there’s a very poignant observation at work about the kind of vulnerability and emotional exposure people go through at such times. We’ve all been there, in a way, and we can immediately relate. That he spends the next 30 minutes crying like a lost puppy would be tiresome, if the filmmakers didn’t manage to make you really believe this guy’s profound and unrelenting desperation to be loved. But they do.

To be fair, however, the film itself, much like it’s main character, is actually a little sloppy. It meanders through a number of clearly ad-libbed sequences with little concern for continuity or cleanliness. The story draws out to become a tad flabby. Though populated (like all Apatow productions) with a fabulously funny ensemble cast, it lopes through two or three more emotional epiphanies than are necessary. Even the most despicable, self-absorbed players are given moments to make their cases and show their humanity. It’s something of a double-edged sword. But any slack in these areas can be easily disregarded for the constant barrage of laugh-out-loud lines and situations the story treats us to.

Though “Forgetting Sarah Marshall” may not technically be a great film, it’s certainly a great comedy, and as such, has some deep and unpredictable insights into the human condition. If you dare go see it with an ex, you might find that forgiving is really at the heart of “Forgetting.”