tyle>
</head>
<body>

<div class="test"><div id="box" lang="en-GB-scouse">&#xA0;</div></div>

<script>
"use strict";
test(() => {
  assert_false(document.getElementById("box").matches("#box[lang='en-GB']"));
}, "A lang= value with multiple subtags will NOT match a lang attribute value with multiple subtags if the latter has more subtags, even if the first two subtags are the same.");
</script>

<div id='log'></div>

</body>
</html>
