Index: openacs-4/packages/acs-templating/tcl/tag-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/acs-templating/tcl/tag-procs.tcl,v
diff -u -r1.10 -r1.11
--- openacs-4/packages/acs-templating/tcl/tag-procs.tcl	31 Jan 2005 21:03:19 -0000	1.10
+++ openacs-4/packages/acs-templating/tcl/tag-procs.tcl	2 Feb 2005 21:32:28 -0000	1.11
@@ -161,18 +161,22 @@
         append condition "\[empty_string_p $arg1\]"
       } else {
         # substitute array variables
-        regsub {^"@([a-zA-Z0-9_]+)\.([a-zA-Z0-9_.]+)@"$} $arg1 {\1(\2)} arg1
-        # substitute regular variables
-        regsub {^"@([a-zA-Z0-9_:]+)@"$} $arg1 {\1} arg1
+        if {! ( [regsub {^"@([a-zA-Z0-9_]+)\.([a-zA-Z0-9_.]+)@"$} $arg1 {\1(\2)} arg1]
+                || [regsub {^"@([a-zA-Z0-9_:]+)@"$} $arg1 {\1} arg1] ) } {
+          error "IF tag nil test uses string not variable for $arg1"
+        }
         append condition "\[template::util::is_nil $arg1\]"
       }
       set next $i
     }
 
     defined {
       # substitute variable references
-      regsub {^"@([a-zA-Z0-9_]+)\.([a-zA-Z0-9_.]+)@"$} $arg1 {\1(\2)} arg1
-      regsub {^"@([a-zA-Z0-9_:]+)@"$} $arg1 {\1} arg1
+      if { ! ( [regsub {^"@([a-zA-Z0-9_]+)\.([a-zA-Z0-9_.]+)@"$} $arg1 {\1(\2)} arg1]
+               || [regsub {^"@([a-zA-Z0-9_:]+)@"$} $arg1 {\1} arg1] )} { 
+        error "IF tag defined test uses string not variable for $arg1"
+      }
+           
       append condition "\[info exists $arg1\]"
       set next $i
     }