Can a form submit handler return results without using the $_GET array?
You can save $content in a session variable, and then redirect the users to a new page. The page callback of that page will then extract the data from the session data.

$_SESSION['mymodule_content'] = $content;
$form_state['redirect'] = 'form/result';




// The page callback then will execute the following code.
$content = $_SESSION['mymodule_content'];


The pros of using session data are:


There isn't the length limit GET data has
The data will not be visible in the browser address bar
The data can be complex like an array, or an object