<xsl:function name="Qname" as="sequence type" [override="yes" | "no"]> 
function_body 
</xsl:function> 

<xsl:transform  
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform" 
  xmlns:xs="http://www.w3.org/2001/XMLSchema" 
  xmlns:str="http://example.com/namespace" 
  version="2.0" 
  exclude-result-prefixes="str"> 
  
<xsl:function name="str:reverse" as="xs:string"> 
  <xsl:param name="sentence" as="xs:string"/> 
  <xsl:sequence   
     select="if (contains($sentence, ' ')) 
             then concat(str:reverse(substring-after($sentence, ' ')), 
                         ' ', 
                         substring-before($sentence, ' ')) 
             else $sentence"/> 
</xsl:function> 
  
<xsl:template match="/"> 
<output> 
  <xsl:value-of select="str:reverse('DOG BITES MAN')"/> 
</output> 
</xsl:template> 
  
</xsl:transform>