[daisy] Comparing against value returned by extension in an xsl stylesheet

[Nick]

I have a Daisy extension that uses flowscript to query and return a value from a
Daisy document (in this case, a field from the most recently modified document)
and returns it. The xsl for the extension looks something like this:

<xsl:template match="latestDocumentData">
  <xsl:value-of select="ns:searchResult/ns:rows/ns:row/ns:value"/>
</xsl:template>

I then need to modify another xsl stylesheet to change its output based on this
value. What I'm doing now seems to be getting me close, but doesn't quite work:

<xsl:variable name="data">
  <einclude:include src="cocoon:/ext/path/to/callLatestDocumentData"/>
</xsl:variable>

Now, I can display the value using <xsl:copy-of select="$data"/>, but what I
really need to do is use that value to compare against something else. i.e.,
<xsl:if "$data == 'something'".../>

Is there anything else I can do? I can just look up this data myself and insert
it into the cocoon pipeline myself, but I would prefer to have it automated...

In any case, thanks in advance for your help!