I have two questions. I know the $() is documented as a subexpression, but what about the double parenthesis without the $ ? I can’t find its documentation in the about_operators page.
Also I know this is a stupid question, but there are dozens of books on powershell. Are there any on cmd itself. I know that powershell basically abrogates cmd, but I can’t believe all those years there was not a book you could pick up to learn the windows command line.