flex 正则表达式查找xml节点名

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">
<mx:Script>
<![CDATA[
import  mx.controls.Alert;
var xml:XML=<cti>ddddd</cti>;
private function click():void
{
var str:String = "<p1>Helloagain</p1><p2>Hello</p2><p3>ddd</p3><q1>Helloagain</q1><q2>Hello</q2><q3>ddd</q3>";           
for(var i:int=1;i<=3;i++)
{
//var pattern:RegExp =/<p+1>.*?.<\/p+1>/;
var s:String="<p+"+i.toString()+">.*?.<\/p+"+i.toString()+">";

var pattern:RegExp = new RegExp(s);
Alert.show(pattern.exec(str)); // <p>Hello</p>

var strs:String="<q+"+i.toString()+">.*?.<\/q+"+i.toString()+">";
var pattern1:RegExp = new RegExp(strs);
Alert.show(pattern1.exec(str));
}

/* pattern = /<p>.*?<\/p>/s;
Alert.show(pattern.dotall.toString()) // true
Alert.show(pattern.exec(str));  */

}

]]>
</mx:Script>
<mx:Button x="201" y="182" label="Button" click="click()"/>

</mx:Application>