XSLT 2.0 - No separator choice available for AVT

Consider the following XSLT:

<xsl:variable name="test" as="xs:string*">
	<xsl:value-of select="'Foo'"/>
	<xsl:value-of select="'Bar'"/>
	<xsl:value-of select="'Baz'"/>
</xsl:variable>

<xsl:template match="/">
	<div a="{$test}">
		<xsl:value-of select="$test" separator=""/>
	</div>
</xsl:template>

Produces:

<div a="Foo Bar Baz">FooBarBaz</div>

Is there any where to 'turn off' the whitespace separation of the text
nodes in $test, or some technique to use within the AVT to mimic
separator="" - I really don't want to use xsl:attribute :)

cheers
andrew