get path.separator from the extract system properties node

I am trying to configure the Extract System Properties node to give me a flow variable for the path.separator. I cannot figure out how to do this. I am just trying to pass that one variable (path.separator) and nothing else. I have tried under the flow variable tab in the node to set the selectedProps to the variable name path.separator, but I don’t think the variable name has to actually be that. Anyway, I’m not getting the path separator which I expect to be “/”.