Commands run with empty strings as required control codes

The docs say:

when a path is required, the command will not be run at all if that path is not valid

  • Visit the Recycle Bin folder.
  • Create a user command Log with template TEXT/R and this JScript code:
    function OnClick(clickData) {
        DOpus.Output(clickData.func.args.text);
    }
    
  • Create a toolbar button with this code and run it:
    // These 4 print/copy empty strings as the variable.
    @output:{sourcepath$}.
    Log {sourcepath$}.
    Clipboard SET={sourcepath$}.
    
    @output:{=sourcepath$=}.
    
    // These 2 each prevent everything from running.
    // I guess this is what's to be expected.
    //Log {=sourcepath$=}.
    //Clipboard SET={=sourcepath$=}.