这段代码死活看不到错误，究竟哪里错了

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="zh-CN">
<head>
<title>新建网页</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="description" content="" />
<script>
function find(){

var lis=document.getElementsByTagName('li');
var patt=/^\w+@\w+(\.\w+)+$/;
var i=0;

console.log(lis.length);
console.log(lis[1].innerHTML);


while(i<lis.length){
if(patt.exec(lis[i].innerHTML)!==null){
lis[i].style.background='yellow';
}
i++;
}
}
</script>

</head>
<body>
<input type="button" value="标注有邮箱的人" onclick="find();" />
<ul>
<li>张飞</li>
<li>刘备<liubei@qq.com></li>
<li>关羽</li>
<li>赵云<zhaoyun@qq.com></li>
</ul>
</body>
</html>