diff --git a/src/rpn-branch.h b/src/rpn-branch.h
index 217cacb..c9e02f9 100644
--- a/src/rpn-branch.h
+++ b/src/rpn-branch.h
@@ -72,7 +72,7 @@ int rpn_for(branch& myobj)
 	// store symbol with first value
     number num;
     num.set(myobj.farg1);
-    _local_heap->add(string(sym->_value), &num, num.size(), cmd_number);
+    _local_heap.add(string(sym->_value), &num, num.size(), cmd_number);
 
 	return myobj.arg1 + 1;
 }
@@ -99,7 +99,7 @@ int rpn_next(branch& myobj)
 		int type;
 		symbol* var = (symbol*)seq_obj(start_or_for->arg1);
 		// check symbol variable is a number, then increase
-        if (_local_heap->get(string(var->_value), obj, size, type) && (type == cmd_number))
+        if (_local_heap.get(string(var->_value), obj, size, type) && (type == cmd_number))
 			((number*)obj)->_value = myobj.farg1;
 	}
 
@@ -144,7 +144,7 @@ int rpn_step(branch& myobj)
 		int type;
 		symbol* var = (symbol*)seq_obj(start_or_for->arg1);
 		// check symbol variable is a number, then increase
-        if (_local_heap->get(string(var->_value), obj, size, type) && (type == cmd_number))
+        if (_local_heap.get(string(var->_value), obj, size, type) && (type == cmd_number))
 			((number*)obj)->_value = myobj.farg1;
 	}
 
diff --git a/src/rpn-program.h b/src/rpn-program.h
index debcde2..4410f7a 100644
--- a/src/rpn-program.h
+++ b/src/rpn-program.h
@@ -12,7 +12,11 @@ void eval(void)
 		unsigned int size;
 		int type;
         string variable(((symbol*)_stack->back())->_value);
-        if (_local_heap->get(variable, obj, size, type) || _global_heap->get(variable, obj, size, type))
+
+        // mind the order of heaps
+        if (_local_heap.get(variable, obj, size, type)
+                || ((_parent_local_heap != NULL) && _parent_local_heap->get(variable, obj, size, type))
+                || _global_heap->get(variable, obj, size, type))
 		{
             // if variable holds a program, run this program
             if (type == cmd_program)
@@ -50,7 +54,8 @@ void eval(void)
         if (program::parse(prog_text.c_str(), prog) == ret_ok)
         {
             // run it
-            prog.run(*_stack, *_global_heap);
+cout<<"eval: avant run: _local_heap.size = "<<_local_heap.size()<<endl;//lru
+            prog.run(*_stack, *_global_heap, &_local_heap);
         }
     }
 }
diff --git a/src/rpn-store.h b/src/rpn-store.h
index 56f3849..2619d75 100644
--- a/src/rpn-store.h
+++ b/src/rpn-store.h
@@ -20,7 +20,11 @@ void rcl(void)
 	unsigned int size;
 	int type;
     string variable(((symbol*)_stack->back())->_value);
-    if (_local_heap->get(variable, obj, size, type) || _global_heap->get(variable, obj, size, type))
+
+    // mind the order of heaps
+    if (_local_heap.get(variable, obj, size, type)
+            || ((_parent_local_heap != NULL) && (_parent_local_heap->get(variable, obj, size, type)))
+            || _global_heap->get(variable, obj, size, type))
 	{
 		_stack->pop_back();
 		_stack->push_back(obj, size, type);
@@ -37,7 +41,12 @@ void auto_rcl(symbol* symb)
 		void* obj;
 		unsigned int size;
 		int type;
-        if (_local_heap->get(string(symb->_value), obj, size, type) || _global_heap->get(string(symb->_value), obj, size, type))
+        string variable(symb->_value);
+
+        // mind the order of heaps
+        if (_local_heap.get(variable, obj, size, type)
+                || ((_parent_local_heap != NULL) && (_parent_local_heap->get(variable, obj, size, type)))
+                || _global_heap->get(variable, obj, size, type))
         {
             _stack->push_back(obj, size, type);
             if (type == cmd_program)
@@ -58,18 +67,22 @@ void purge(void)
 	ARG_MUST_BE_OF_TYPE(0, cmd_symbol);
 
     string name(((symbol*)_stack->back())->_value);
-    if (_local_heap->erase(name))
+
+    // mind the order of heaps
+    bool done = false;
+    if (!_local_heap.erase(name))
     {
-        //TODO another error
-        ERR_CONTEXT(ret_bad_operand_type);
+        if ((_parent_local_heap != NULL) && (_parent_local_heap->erase(name)))
+            done = true;
+        else if (_global_heap->erase(name))
+            done = true;
     }
     else
-    {
-        if (!_global_heap->erase(name))
-            _stack->pop_back();
-        else
-            ERR_CONTEXT(ret_unknown_variable);
-    }
+        done = true;
+
+    _stack->pop_back();
+    if (!done)
+        ERR_CONTEXT(ret_unknown_variable);
 }
 
 void vars(void)
@@ -79,19 +92,28 @@ void vars(void)
 	int type;
 	string name;
 
-    for (int i=0; i<(int)_local_heap->size(); i++)
+    for (int i=0; i<(int)_global_heap->size(); i++)
     {
-        (void)_local_heap->get_by_index(i, name, (void*&)obj, size, type);
+        (void)_global_heap->get_by_index(i, name, (void*&)obj, size, type);
+        cout<<"var "<<i+1<<": name '"<<name<<"', type "<<cmd_type_string[type]<<", value ";
+        obj->show();
+        cout<<endl;
+    }
+    if (_parent_local_heap != NULL)
+    {
+        for (int i=0; i<(int)_parent_local_heap->size(); i++)
+        {
+            (void)_parent_local_heap->get_by_index(i, name, (void*&)obj, size, type);
+            cout<<"local var "<<i+1<<": name '"<<name<<"', type "<<cmd_type_string[type]<<", value ";
+            obj->show();
+            cout<<endl;
+        }
+    }
+    for (int i=0; i<(int)_local_heap.size(); i++)
+    {
+        (void)_local_heap.get_by_index(i, name, (void*&)obj, size, type);
         cout<<"local var "<<i+1<<": name '"<<name<<"', type "<<cmd_type_string[type]<<", value ";
         obj->show();
         cout<<endl;
     }
-
-    for (int i=0; i<(int)_global_heap->size(); i++)
-	{
-        (void)_global_heap->get_by_index(i, name, (void*&)obj, size, type);
-		cout<<"var "<<i+1<<": name '"<<name<<"', type "<<cmd_type_string[type]<<", value ";
-		obj->show();
-		cout<<endl;
-	}
 }
diff --git a/src/rpn-string.h b/src/rpn-string.h
index 4158ec9..8d31849 100644
--- a/src/rpn-string.h
+++ b/src/rpn-string.h
@@ -29,6 +29,6 @@ void strout()
     if (program::parse(entry.c_str(), prog) == ret_ok)
 	{
 		// run it
-        prog.run(*_stack, *_global_heap);
+        prog.run(*_stack, *_global_heap, &_local_heap);
 	}
 }
diff --git a/src/rpn.cpp b/src/rpn.cpp
index 3d6e906..40e2fda 100644
--- a/src/rpn.cpp
+++ b/src/rpn.cpp
@@ -355,9 +355,8 @@ public:
 	program() { }
 
 	// run this program
-    ret_value run(stack& stk, heap& hp, heap* local_hp = NULL)
+    ret_value run(stack& stk, heap& hp, heap* parent_local_hp = NULL)
 	{
-        heap local_heap;
         bool go_out = false;
 		ret_value ret = ret_ok;
 		cmd_type_t type;
@@ -368,12 +367,8 @@ public:
         // global heap comes from outside
         _global_heap = &hp;
 
-        // local heap can come from outside
-        // if not, set a new local heap
-        if (local_hp != NULL)
-            _local_heap = local_hp;
-        else
-            _local_heap = &local_heap;
+        // parent local heap comes from outside
+        _parent_local_heap = parent_local_hp;
 
         _err = ret_ok;
         _err_context = "";
@@ -693,9 +688,12 @@ public:
 private:
 	ret_value _err;
 	string _err_context;
-	stack* _stack;
+
+    stack* _stack;
+
     heap* _global_heap;
-    heap* _local_heap;
+    heap _local_heap;
+    heap* _parent_local_heap;
 
 	// helpers for keywords implementation
 	floating_t getf()