<xsl:variable name="var">
			<xsl:element name="root">
				<xsl:element name="subroot">
					<xsl:apply-templates select="file_entry"/>
				</xsl:element>
			</xsl:element>
		</xsl:variable>



that could more easily be written

	<xsl:variable name="var">
			<root>
				<subroot>
					<xsl:apply-templates select="file_entry"/>
				</subroot>
			</root>
		</xsl:variable>

For your given input, the root element does not have any file_entry
elements so $test is the document
<root><subroot/></root>

Your key matches on subroot elements using the value of ccc, but this
subroot does not have a ccc element so the key returns nothing, asl you
comment.

David

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