master.xml

<data>
  <hello>List or not to list</hello>
  <entry>
    <item>1</item>
    
  </entry>
</data>

master.xsl

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">

  <xsl:output method="xml" indent="yes" />

  <xsl:template match="/">
    <h1>
      <xsl:value-of select="data/hello" />
    </h1>
    
    <xsl:choose>
      <xsl:when test="count(//data/entry/item) &gt; 1">
    <xsl:text>This is multiple items</xsl:text>
  </xsl:when>
  <xsl:otherwise>
    <xsl:text>This is a single item</xsl:text>
  </xsl:otherwise>
</xsl:choose>
    
  </xsl:template>


  
  
</xsl:stylesheet>