Template match with parameters?

Hi people,
a question for a simple answer... or a complicated alternative.

Is it possible to invoke a template match passing an arbitrary parameter?
Something like this in which, when occur the <elem2> element is it
possible to pass it an x parameter.

=================================================

 <xsl:template match="root">
   <root>
     <xsl:apply-templates/>
   </root>
 </xsl:template>

 <xsl:template match="@*|node()">
   <xsl:copy>
     <xsl:apply-templates select="@* | node()"/>
   </xsl:copy>
 </xsl:template>

 <xsl:template match="elem2">
   <xsl:param name ="x"/>
<<<<<<<<<<<=============== LOOK HERE !!!

   <elem2>new_<xsl:value-of select="x$"/></elem2>
 </xsl:template>

=================================================

The x parameter should be provided by some other template.

If should be possible reset a variable value, I could define a global
variable and change is value before to process a new <elem2>
occurence, but since is not possible I need an alternative.

Thanks in advance for your help.

Ciao. Nicola