How to use the @glimmer/vm.Op.Dup function in @glimmer/vm

stack.push(PrimitiveReference.create(check(stack.pop(), CheckPrimitive)));
  },
  OpcodeKind.Mut
);

APPEND_OPCODES.add(
  Op.ReifyU32,
  vm => {
    let stack = vm.stack;
    stack.push(check(stack.peek(), CheckReference).value());
  },
  OpcodeKind.Mut
);

APPEND_OPCODES.add(
  Op.Dup,
  (vm, { op1: register, op2: offset }) => {
    let position = check(vm.fetchValue(register), CheckNumber) - offset;
    vm.stack.dup(position);
  },
  OpcodeKind.Mut
);

APPEND_OPCODES.add(
  Op.Pop,
  (vm, { op1: count }) => {
    vm.stack.popN(count);
  },
  OpcodeKind.Mut
);

APPEND_OPCODES.add(

switch (value) {
        case 0: stack.push(false); break;
        case 1: stack.push(true); break;
        case 2: stack.push(null); break;
        case 3: stack.push(undefined); break;
      }
      break;
  }
});

APPEND_OPCODES.add(Op.PrimitiveReference, vm => {
  let stack = vm.stack;
  stack.push(PrimitiveReference.create(check(stack.pop(), CheckPrimitive)));
});

APPEND_OPCODES.add(Op.Dup, (vm, { op1: register, op2: offset }) => {
  let position = check(vm.fetchValue(register), CheckNumber) - offset;
  vm.stack.dup(position);
});

APPEND_OPCODES.add(Op.Pop, (vm, { op1: count }) => {
  vm.stack.pop(count);
});

APPEND_OPCODES.add(Op.Load, (vm, { op1: register }) => {
  vm.load(register);
});

APPEND_OPCODES.add(Op.Fetch, (vm, { op1: register }) => {
  vm.fetch(register);
});