It looks like we can't sepecify several parameters on the command line
using --param.

Test case:

* Stylesheet (params.xsl):

<?xml version= "1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<xsl:param name="param1"/>
<xsl:param name="param2"/>

	<xsl:template match="/">
		<xsl:if test="$param1">
			PARAM1: <xsl:value-of select="$param1"/>
		</xsl:if>
		<xsl:if test="$param2">
			PARAM2: <xsl:value-of select="$param2"/>
		</xsl:if>
		END
	</xsl:template>


</xsl:stylesheet>

* xml file (test.xml):

<?xml version= "1.0"?>

 <doc/>

* test:

[rchaillat@pc-1229 modules]$ xsltproc --param param1 test1 --param param2
test2 params.xsl test.xml 
<?xml version="1.0"?>

                        PARAM1: test1
                END