diff --git a/addon/lib/querystring.tcl b/addon/lib/querystring.tcl
new file mode 100644
index 0000000..bd1f01f
--- /dev/null
+++ b/addon/lib/querystring.tcl
@@ -0,0 +1,9 @@
+catch {
+  set input $env(QUERY_STRING)
+  set pairs [split $input &]
+  foreach pair $pairs {
+    if {0 != [regexp "^(\[^=]*)=(.*)$" $pair dummy varname val]} {
+      set $varname $val
+    }
+  }
+}
diff --git a/addon/lib/session.tcl b/addon/lib/session.tcl
new file mode 100644
index 0000000..eb183a6
--- /dev/null
+++ b/addon/lib/session.tcl
@@ -0,0 +1,13 @@
+#!/bin/tclsh
+
+load tclrega.so
+
+proc check_session sid {
+    if {[regexp {@([0-9a-zA-Z]{10})@} $sid all sidnr]} {
+        set res [lindex [rega_script "Write(system.GetSessionVarStr('$sidnr'));"] 1]
+        if {$res != ""} {
+            return 1
+        }
+    }
+    return 0
+}