Randomize XML with xsltproc

I have a simple xml file:

<headlines>
  <headline>
  ...
  </headline>
  <headline>
  ...
  </headline>
  <headline>
  ...
  </headline>
</headlines>

All I want to do is shuffle the order in which headlines appear. I've been fooling around how this template should look, but I can't get it working.

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:template match="/headline">
<xsl:for-each select="headline">
  __not sure what to do here? rand() isn't a thing?__

One way to do this would be to use the function generate-id() as a sorting criterion. Suppose you have the following input:

<?xml version="1.0" encoding="ISO-8859-1"?>
<headlines>
  <headline>
    Limburg
  </headline>
  <headline>
    Fukushima
  </headline>
  <headline>
    Große Koalition
  </headline>
  <headline>
    Flugzeugabsturz
  </headline>
</headlines>

With this XSLT you can "randomize" the output:

<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet 
    version="1.0"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

  <xsl:output method="xml" encoding="ISO-8859-1"/>

  <xsl:template match="/headlines">
    <headlines>

      <xsl:for-each select="headline">
        <xsl:sort select="generate-id(.)"/>

        <headline id="{generate-id(.)}">
          <xsl:copy-of select="./text()"/>
        </headline>

      </xsl:for-each>

    </headlines>
  </xsl:template>
</xsl:stylesheet>

The result is

<?xml version="1.0" encoding="ISO-8859-1"?>
<headlines><headline id="idm3928">
    Limburg
  </headline><headline id="idm5512">
    Flugzeugabsturz
  </headline><headline id="idm5704">
    Große Koalition
  </headline><headline id="idm5920">
    Fukushima
  </headline></headlines>

Three things should be noted:

The output of attribute "id" in the headline tag is not necessary. This is just for visualizing the sort criterion.
The sorting order depends on the xslt processor used (in this case a Debian xsltproc).
It's not really "random". However, the processor xsltproc actually chooses new ids with every call so in fact the headlines get "shuffled". :-)