Redirect to Page after Login (with variable)

Question

I want to redirect subscribers to a special page after login to my WordPress Site ("http://www.my-cool-page.com/coolpeople") where "coolpeople" is a regular WordPress page. This is my code to redirect only the "subscribers":

$internStart = 'evenmorecoolpeople';
function loginRedirect( $redirect_to, $request_redirect_to, $user ) {
    if ( is_a( $user, 'WP_User' ) && $user->has_cap( 'edit_posts' ) === false ) {
        echo 'return URL: ' . home_url('/') . $internStart; die ();
        return home_url();
    }
    return $redirect_to;
}
add_filter( 'login_redirect', 'loginRedirect', 10, 3 );

Now I want to replace "coolpeople" with a variable like:

$internStart = 'evenmorecoolpeople';

but ...

return home_url($internStart);

or ...

return home_url('/') . $internStart;

Does not work. Any Idea?