XML : How To Compare Two Comma Seprated Lists and Removing Matching Values using XSLT 1.0

I have two variables which contain comma separated values:-

    <xsl:variable name="Include-Cities" select="'London, Paris, Washington, Tokyo'"/>    <xsl:variable name="Exclude-Cities" select="'Paris, Tokyo'"/>    

I have a requirement to remove the values in $Include-Cities which match those found in $Exclude-Cities, so in a way I am subtracting those values from the $Include-Cities variable and outputting the result.

I have looked around the web and found the following example which provides search and replace functionality and which works if the order of the cities in $Exclude-Cities matches the order in $Include-Cities, but fails if the order of values if different.

I am stuck as the values in both lists can change daily and i will never know what those values are, therefore i don't think performing a sort (if its possible) will work.

The example i found:-

  <xsl:template name="replace-string">      <xsl:param name="text"/>      <xsl:param name="replace"/>      <xsl:param name="with"/>      <xsl:choose>        <xsl:when test="contains($text,$replace)">          <xsl:value-of select="substring-before($text,$replace)"/>          <xsl:value-of select="$with"/>          <xsl:call-template name="replace-string">            <xsl:with-param name="text" select="substring-after($text,$replace)"/>            <xsl:with-param name="replace" select="$replace"/>            <xsl:with-param name="with" select="$with"/>          </xsl:call-template>        </xsl:when>        <xsl:otherwise>          <xsl:value-of select="$text"/>        </xsl:otherwise>      </xsl:choose>    </xsl:template>    

Then i call the template using:-

  <xsl:call-template name="replace-string">      <xsl:with-param name="text" select="$Include-Cities"/>      <xsl:with-param name="replace" select="$Exclude-Cities" />      <xsl:with-param name="with" select="''"/>   </xsl:call-template>    

I have also looked at examples of tokenizing the values and comparing that way but have had no joy whatsoever.

I know there are string comparsion functions available in 2.0 but I am restricted to using XSLT 1.0.

I am an XSLT noob so can anyone help please?

Any help would be most appreciated