difference in regexp matches() and analyze-string

<doc>
    <al>1. eerste alinea</al>
    <al>2. tweede alinea</al>
    <al>3. tweede alinea</al>
</doc>

  <xsl:template match="/">
    <xsl:apply-templates />
  </xsl:template>

  <xsl:template match="al">
    <xsl:variable name='txt' select="./text()"/>
    <xsl:variable name='re2'
          select="concat('^(', '2\.)',  '\s+(.*)$')"
                      as="xs:string"/>

    <xsl:if test="matches($txt,  $re2)">
      <xsl:text>MATCH</xsl:text>
    </xsl:if>
        <xsl:analyze-string select="$txt" regex="$re2" >
          <xsl:matching-substring>
            <match/>
          </xsl:matching-substring>

          <xsl:non-matching-substring>
            <no-match/>
          </xsl:non-matching-substring>
        </xsl:analyze-string>
  </xsl:template>

<?xml version="1.0" encoding="UTF-8"?>
        <no-match/>
        MATCH<no-match/>
        <no-match/>