fn:contains -> multiple strings to compare with

An XSLT user asked following question on xsl-list:

I want to have something that does this: contains('$d/ris:organ/text()', 'Hamburg' or 'Koblenz' or 'xxx'...) ===> Compare 1 String with multpile strings.

instead of: contains('$d/ris:organ/text()','Hamburg') or contains('$d/ris:organ/text()','Koblenz')...

Andrew Welch suggested following answer:

some $x in ('Hamburg', 'Koblenz', 'xxx') satisfies
contains($d/ris:organ/text(), $x)

This uses the XPath 2.0 quantified expression, "some".

This is cool.

I was prompted to share Andrew's answer here, because I thought of a lengthy and perhaps inefficient solution for this (I feel a bit stupid, actually :) ):

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                xmlns:xs="http://www.w3.org/2001/XMLSchema"
                xmlns:my="http://my-functions"
                version="2.0">

 <xsl:output indent="yes" omit-xml-declaration="yes" />

 <xsl:template match="/">
  <xsl:variable name="str" select="'hello xxx dd'" />
  <xsl:variable name="list" select="('Hamburg','Koblenz','xxx')" />

  <xsl:if test="my:contains($str, $list)">
     matches
  </xsl:if>

 </xsl:template>

 <!-- a custom 'contains' implementation -->
 <xsl:function name="my:contains" as="xs:boolean">
  <xsl:param name="str" as="xs:string" />
  <xsl:param name="list" as="xs:string+" />

  <xsl:variable name="temp" as="xs:boolean*">
    <xsl:for-each select="$list">
      <xsl:if test="contains($str, .)">
        <xsl:sequence select="xs:boolean('true')" />
      </xsl:if>
    </xsl:for-each>
  </xsl:variable>

  <xsl:sequence select="if ($temp[1] = xs:boolean('true')) then
xs:boolean('true') else xs:boolean('false')" />

 </xsl:function>

</xsl:stylesheet>