Help using the session table

[dannyb2100]

Hey all, ok I've created a plugging at hook Global_start.

if ($vbulletin->session->vars['email'] == 0)
{
$varemail = $bbuserinfo[email];
//Add the user email to the session var
    $vbulletin->session->set('email', $varemail);

}

Whats wrong someone help me out as its not setting the information ?
sorry if its so simple and easy, only just getting the hang of the way VBB is coded,

Thanks again VBB,

Dan.