Index: /trunk/Ohana/src/opihi/lib.shell/stack_math.c
===================================================================
--- /trunk/Ohana/src/opihi/lib.shell/stack_math.c	(revision 14516)
+++ /trunk/Ohana/src/opihi/lib.shell/stack_math.c	(revision 14517)
@@ -1156,7 +1156,17 @@
   char line[512];
 
+  /* only 'N' and 'E' are allowed for WW_binary operations. anything else is either a
+   syntax error or is a string which looks like a math expression. */
+
+  if ((op[0] != 'N') && (op[0] != 'E')) {
+    sprintf (line, "error: op %c not defined for string operations!", op[0]);
+    push_error (line);
+    return (FALSE);
+  }
+
   /* evaluate stack will only call WW_binary with one numerical value,
      and only in the case that the string did not parse to a number 
      thus: string == number -> false */
+
   if (!strncasecmp (&V1[0].type, "S", 1)) {
     value = (op[0] == 'N');