document() path created from xml

I'm trying to load an xml document with document(), every file has an id and
I need to take this id from the originaly loaded xml, I tried this with a
variable but I can't get it to work, this one of the xsls I tried:


<xsl:variable name="path">
   document('../data/institutions/institutions_country0.xml')/institutions
</xsl:variable>

<xsl:apply-templates select="$path"/>

A related question; is there any way of seeing what the result of an
expression is? I know I'm doing something wrong but "Reference to variable
or parameter 'path' must evaluate to a node list" is a bit vague, I would
like to see what's actually happening...


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