Error in fb_example.module if statement is setting value instead of comparing values = / ==

This is line 256 of fb_example.module

        if ($fbu = fb_facebook_user()) {
          // The user has connected (as opposed to logged out).  Let's redirect
          // them to our 'welcome' page.  Replace 'welcome' with the path you
          // really want.
          $url = url('welcome',
                     array('absolute' => TRUE, 'fb_canvas' => fb_is_canvas()));
          // We return javascript to be evaluated by fb.js.
          $return[] = "FB_JS.reload('$url');";
        }

I am wanting to verify if the $fbu = fb_facebook_user() is meant to compare the values, or if it is meant to set the value of $fbu and if for some reason the operation returns false to not run the bit of code? I don't see that $fbu is used anywhere else in the function so it is a bit uncertain.

It looks like a common error, but I'm not certain what the side effects / testing of this have been...