code: public Object getVariable(Object key) {
  		Object object = null;
  
  		for (int i = working.size() - 1; i >= 0; --i) {
  			Map<Object, Object> map = working.get(i);
  			object = map.get(key);
  			if (object != null)
  				break;
  		}
  		if (object == null)
  			object = global.get(key);
  
  		return object;
  	}
docs: get a variable, first from the highest block hierarchy down to the global
  variables.
  
  @param key
  name of the variable
  @return value of the variable