Is this your way of saying that I can in fact use a placeholder for that specific value and it will solve my problem?

Yes. I thought you knew that.

I just read about undef today and wasn't sure if it fit my situation or not.

It sounds like you didn't read the docs for do.

The list of values to be bound starts at the third parameter. If one wants to pass values to be bound, one needs to specifies a value for do's second parameter. The undef is the default value for that parameter.