----------------------------------------------------------------------
Package/Module/Helper/Data.php
----------------------------------------------------------------------

class Package_Module_Helper_Data extends Mage_Core_Helper_Abstract
{
    /*
     * Inserts array at given position and shifts elements down
     *
     * @param integer $position
     * @param array $array
     * @param array $element
     */
    public function array_insert($position=null,&$array,$element) {
        if (count($array) == 0) {
            $array[] = $element;
        }
        elseif (is_numeric($position) && $position < 0) {
            if((count($array)+position) < 0) {
                $array = array_insert($array,$element,0);
            }
            else {
                $array[count($array)+$position] = $element;
            }
        }
        elseif (is_numeric($position) && isset($array[$position])) {
            $part1 = array_slice($array,0,$position,true);
            $part2 = array_slice($array,$position,null,true);
            $array = array_merge($part1,array($position=>$element),$part2);
            foreach($array as $key=>$item) {
                if (is_null($item)) {
                    unset($array[$key]);
                }
            }
        }
        elseif (is_null($position)) {
            $array[] = $element;
        }
        elseif (!isset($array[$position])) {
            $array[$position] = $element;
        }
        $array = array_merge($array);
        return $array;
    }
}

----------------------------------------------------------------------
Package/Module/Block/Page/Html/Head.php
----------------------------------------------------------------------

class Package_Module_Block_Page_Html_Head extends Mage_Page_Block_Html_Head
{
    
    public function addJs($name, $params = "", $sort_order = null)
    {
        $this->addItem('js', $name, $params, null, null, $sort_order);
        return $this;
    }
    
    public function addItem($type, $name, $params=null, $if=null, $cond=null, $sort_order = null)
    {
        if ($type==='skin_css' && empty($params)) {
            $params = 'media="all"';
        }

        // If sort order is defined then do it
        if($sort_order>=0) {
            $helper = Mage::helper('jquerylib');
            $helper->array_insert($sort_order, $this->_data['items'],array(
                'type'   => $type,
                'name'   => $name,
                'params' => $params,
                'if'     => $if,
                'cond'   => $cond
            ));

        // Or else append item
        } else {
            $this->_data['items'][$type.'/'.$name] = array(
                'type'   => $type,
                'name'   => $name,
                'params' => $params,
                'if'     => $if,
                'cond'   => $cond,
            );
        }
        return $this;
    }
}