Since it is windows specific you will have to research more regarding windows than perl. Lookup Hook functions in the win32 api reference at MSDN. They will allow you to snoop mouse events system-wide. You can use the Win32::API module for this direct API access.

You may have a hard time telling which button is pressed because manipulating or querying controls inside another window (that your program does not own) is not permitted.

You can probably get more help at a windows forum as suggested.