<xsl:stylesheet version="1.0" extension-element-prefixes="cred"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:cred  ="http://www.some.com/xsl/cred"
  >

  <xsl:output method="html"/>

  <xsl:template match="/">
	<xsl:variable name="dbg1" select="cred:myfunc()"/>
	<xsl:value-of select="concat('===]',$dbg1,'[===')"/>
  </xsl:template>

  <xsl:include href="layout.xsl"/>  
</xsl:stylesheet>
