try to capture the referrer with javascript than pass that value into your perl script like this:

<SCRIPT language=javascript>
//<!--var x;
x="";
x+="<a href='http://www.xyz.com'>";
x+="<img src='http://www.xyz.com/cgi-bin/tracker.cgi?m=CSP&page=";
x+=escape(location.pathname)+"&ref="+escape(document.referrer)+"&ua="+
+escape(navigator.userAgent)+"&plat=";
x+=escape(navigator.platform)+"&cooks="+escape(navigator.cookieEnabled
+)+"&cpu=";
x+=escape(navigator.cpuClass)+"&java="+escape(navigator.javaEnabled())
++"'></a>";
document.write(x);
//-->
</script>
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