Pipe Question

How could I use a pipe for this predicate to specifiy the inclusion of
ALL where $match does not exist (is empty)?

[@sComponentObjectName=$match]

This written out verbose would be:

<xsl:choose>
  <xsl:when test="$match">
     ... apply-templates with above predicate ...
  </xsl:when>
  <xsl:otherwise>
    ... apply-templates without above predicate ...
  </xsl:otherwise>
</xsl:choose>