You don't say what you want to achieve, but I assume it's to output a series of <a href="...">
. If so, the following works:
<xh:html xmlns:xh="http://www.w3.org/1999/xhtml"
xmlns:xf="http://www.w3.org/2002/xforms">
<xh:head>
<xf:model>
<xf:instance id="temp">
<temp>
<links>
<item>ex1</item>
<item>ex2</item>
<item>ex3</item>
<item>ex4</item>
</links>
</temp>
</xf:instance>
</xf:model>
</xh:head>
<xh:body>
<xf:repeat ref="instance('temp')/links/item">
<xh:a href="http://example.com/{.}">Roll</xh:a>
</xf:repeat>
</xh:body>
</xh:html>