Return value from a template 2...

I want to return a value from a template(getIdList). The returned
value is saved in a variable ($idList) and is a string wich is the
concatenation  of my nodes id : id1,id2,id3,...
I use this code wich is not working... i got nothing when i display
the variable value...!!

Here's my code:

<?xml version="1.0"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:output indent="yes" method="html" omit-xml-declaration="no"
encoding="ISO-8859-1" />
<xsl:param name="delimiter" select="','"/>

       <xsl:template match="/root">
               <xsl:variable name="idList">
                       <xsl:call-template select="/root/vid" name="getIdList" />
               </xsl:variable>
               <xsl:value-of select="$idList"/>
       </xsl:template>

       <xsl:template match="/root/vid" name="getIdList">
               <xsl:for-each select=".">
                       <xsl:variable name="var"
select="concat($var,ids, $delimiter)"/>
               </xsl:for-each>
               <xsl:value-of select="$var"/>
       </xsl:template>

</xsl:stylesheet>

What's wrong in it? is there another simple way to get what i want?