access argument

Let's say I have a custom module as "mycustommenu" and have a hook menu and hook perm as
function mycustommenu_perm {
return array('hi','hello','welcome','bye');
}

function mycustommenu_menu() {
global $user;
$items['mycustommenu'] = array(
'title' => 'custom menu',
'page callback' => 'mycustommenu_welcome',
'page arguments' => array($user->name),
'access callback' => 'user_access',
'access arguments' => array('welcome'),
'type' => MENU_NORMAL_ITEM,
);

and the callback function is

function mycustommenu_welcome($uname='')
{