storing the result of a transformation in a param and

Hello all,

If I store the result of a transformation into a variable, is there a way to
check this variable to see if it contains an element or nothing?

For example:

<xsl:template name="item">
  <xsl:param name="content">
    <xsl:apply-templates/>
  </xsl:param>
  <xsl:copy-of select="$content"/>
</xsl:template>

The copy-of element returns $content which is:

<world>hello</world>

What if the apply-templates element returned nothing and $content is empty.
Is there a way to check for this situation?

Thanks a lot.

J-F