This variable is a result tree fragment. In XSLT 1.0 you aren't allowed to
probe inside a result tree fragment using path expressions such as
<xsl:with-param name="warning" select="$warning" />
> I don't like it. I'd rather do it in one fell swoop, a la:
> <xsl:call-template name="warning">
> <xsl:with-param name="warning">
> <warning>New contacts may only be added to active
> <xsl:with-param name="level">3</xsl:with-param>
This code is completely equivalent to what you had before.
> But my template complains: Reference to variable or parameter
> 'warning' must evaluate to a node list.
It's right to complain. You can't use a result tree fragment as an operand
It was wrong not to complain before, when you used the xsl:variable.
What processor are you using?
> Also, I'm all about syntax efficiency. Are there any other
> shortcuts I could take besides the one I'm looking for?
Well, if you want to make full use of result tree fragments / temporary
trees, your best bet is to move to XSLT 2.0.