I know you have anonymous functions in XPath 3.0, but you cannot use
instructions in them, you'd have to put them in an `xsl:function`, and
by then all the fun is gone. Something like this (nevermind the name):

<xsl:variable name="myFn">
   <xsl:delegate>
      <xsl:param name="a"/>

      <xsl:call-template name="foo"/>
   </xsl:delegate>
</xsl:variable>

<xsl:sequence select="$myFn(5)"/>
--
Max Toro