Counting Word Occurences

In an attempt to implement simple keyword searching, I did the following to
count the number of occurences of the user's keyword in the <abstract>
element. What I would like to do now is count the number of times that the
keyword occurs in the context node's child <abstract> as well as all
descendant <div> element's <abstract> children. I was hoping it would be as
simple as defining the variable "text" as
"descendant-or-self::div/abstract", but that only gave me the count for the
first <abstract> element. I think what I'm trying to do is concatenate the
text of all the descendant <abstract> elements into a single string. Or am I?

<doc>
  <div>
    <title></title>
    <abstract\>foo bar</abstract>
    <div>
      <title></title>
      <abstract\>foo bar</abstract>
    </div>
  </div>
</doc>

<xsl:param name="keyword" select="foo"/>

<xsl:template match="div" mode="toc">
  <xsl:variable name="text" select="div/abstract"/>
  <xsl:if test="contains($text, $keyword)">
    <xsl:call-template name="count">
      <xsl:with-param name="text" select="$text"/>
      <xsl:with-param name="keyword" select="$keyword"/>
    </xsl:call-template>
  </xsl:if>
</xsl:template>

<xsl:template name="count">
  <xsl:param name="text"/>
  <xsl:param name="keyword"/>
  <xsl:choose>
    <xsl:when test="contains($text, $keyword)">
      <xsl:variable name="occurence" select="substring-before($text,
$keyword)"/>
      <xsl:variable name="remainder" select="substring-after($text,
$keyword)"/>
      <xsl:variable name="total">
	<xsl:call-template name="count">
	  <xsl:with-param name="text" select="$remainder"/>
	  <xsl:with-param name="keyword" select="$keyword"/>
	</xsl:call-template>
      </xsl:variable>
      <xsl:value-of select="$total + '1'"/>
    </xsl:when>
    <xsl:otherwise>0</xsl:otherwise>
  </xsl:choose>
</xsl:template>


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