Why do you think you need to double the backslash on Windows? It's not because of Windows, it's because Perl uses the backslash as the escape character.

In your first attempt, Perl was trying to escape "p" and "l", converting regular characters to special characters, but then the path you were trying to reach didn't exists.

In your second attempt, you double the backslash, basically you escape the special character "\" and it becomes a regular character, so Perl really see a backslash, and the path now exists.

But, in Perl on Windows, you can also use the forward slash "/" in file paths.

Hope this help you understand what was going on internally.