XSLT 3.1 that keeps both Saxon EE and HE happy and to

I have quite a few attributes whose values are space delimited tokens. Saxon
EE bknowsb they are lists of tokens since the schema does have them a
lists so they can be constrained and validated at the XSD level.
tokenize(./@someAttribute) works great in HE but bombs in EE with A sequence
of more than one item is not allowed as the first argument of fn:tokenize()

This feels like it should be obvious and trivial but has been irritating me
for a while now.

 Below is an example instance, schema, and xslt that work fine in HE but not
EE. I get why it chokes for EE but not how to make it always work. This is a
trivial example my real problems tend to be using this in some ugly schematron
test so a more general purpose solution like I guess a function smart enough
to know what to do? I tried that a bit but it got dumber and dumber the longer
I poked at it. So back to just requirements and hoping one of has the obvious
answer.

Given the sample xml

<?xml version="1.0" encoding="UTF-8"?>
<sample xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:noNamespaceSchemaLocation="Example.xsd">
    <stuff country='USA'/>
    <stuff country='USA GBR'/>
    <stuff country='GBR CAN'/>
</sample>

Schema
?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified">

  <xs:element name="sample">
    <xs:complexType>
      <xs:sequence>
        <xs:element maxOccurs="unbounded" ref="stuff"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>

  <xs:element name="stuff">
    <xs:complexType>
      <xs:attribute name="country" use="required" type="countryListType"/>
    </xs:complexType>
  </xs:element>

  <xs:simpleType name="countryListType">
    <xs:restriction>
      <xs:simpleType>
        <xs:list itemType="countryType"/>
      </xs:simpleType>
      <xs:maxLength value="3"/>
    </xs:restriction>
  </xs:simpleType>

  <xs:simpleType name="countryType">
    <xs:restriction base="xs:token">
      <xs:enumeration value="USA"/>
      <xs:enumeration value="GBR"/>
      <xs:enumeration value="CAN"/>
    </xs:restriction>
  </xs:simpleType>

</xs:schema>

and XSL
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
    xmlns:math="http://www.w3.org/2005/xpath-functions/math"
    xmlns:xd="http://www.oxygenxml.com/ns/doc/xsl"
    exclude-result-prefixes="xs math xd"
    version="3.1">

    <xsl:output indent="yes"/>

    <xsl:template match="stuff">
        <xsl:copy>
            <xsl:apply-templates select="@country"/>
        </xsl:copy>
    </xsl:template>

    <xsl:template match="@country">
        <xsl:for-each select="tokenize(.)">
            <country><xsl:value-of select="current()"/></country>
        </xsl:for-each>
    </xsl:template>

</xsl:stylesheet>

with HE I get
<?xml version="1.0" encoding="UTF-8"?>
<stuff xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
   <country>USA</country>
</stuff>
<stuff xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
   <country>USA</country>
   <country>GBR</country>
</stuff>
<stuff xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
   <country>GBR</country>
   <country>CAN</country>
</stuff>


With EE

System ID: /Volumes/DNI_SVN/SaxonHE-EE/example.xsl
Severity: fatal
Problem ID: XPTY0004
Description: A sequence of more than one item is not allowed as the first
argument of fn:tokenize() ("USA", "GBR")
Start location: 18:44
URL: http://www.w3.org/TR/xpath20/#ERRXPTY0004