asclass VarContext {
  gettable VarContext parent;

  *() {}
  *(VarContext *parent) {}
  
  abstract O get(S name);
  
  abstract void set aka put(S name, O value);

  abstract AutoCloseable tempSet aka tempPut(S name, O value);
  
  // either undefines variable completely or just sets variable to null
  abstract void unset(S name);
  
  abstract MapSO varMap();
  
  void printMe {
    pnl(varMap());
    print(+parent);
  }
  
  // mechanism for returning from a script
  
  settable O exitFromScript;
  settable O returnValue;
  bool exiting() { ping(); ret exitFromScript != null; }
}