xslt create a variable from external xml file

I have a need to determine what environment I'm working on without hardcoding
the differences in the large xslt file.
I have tried

<xsl:variable name="externalDoc" select="document('inc/env.xml')"/>

File content
<?xml version="1.0" encoding="UTF-8"?>
<root>
    <environment>test</environment>
</root>

And in the main xslt file I use, I just want to add a T at the end.

<xsl:choose>
  <xsl:when test="$externalDoc/environment = 'test'">
    <xsl:text>T</xsl:text>
  </xsl:when>
  <xsl:when test="$externalDoc/environment = 'prod'">
    <xsl:text></xsl:text>
  </xsl:when>
</xsl:choose>




Phil Legault
RDx Platform Lead