No, really, this is the code for the new keyword parsing.

luprex/core/cpp/planemap.hpp

@@ -131,8 +131,8 @@ public:
     
     // Convert a lua table into a scan configuration.
     //
-    // If there is an error in the configuration, returns an
-    // error message, otherwise returns empty string.
+    // If there is an error in the configuration, 
+    // throws a lua error message.
     //
     // Caution: if this detects the configuration flag 'near',
     // then it stores the near ID.  However, it doesn't fetch
@@ -141,7 +141,7 @@ public:
     // and plane.  This is admittedly ugly, but it eliminates
     // a dependency on the world module.
     //
-    eng::string configure(const LuaStack &LS, LuaSlot slot);
+    void configure(LuaKeywordParser &kw);
 
     void set_bbox_given_center_radius(const util::XYZ &center, float r) {
         set_center(center);