Since I've been primarily working in the world of Windows, I've been using Win32::GUI. To help speed up the development, I've been using the GUI Loft. It allows me to quickly set up the GUI look and appearance. However, I then have the to generate the code by hand and refer back to the GUI Loft for the size and location coordinates.

I can't advocate that Win32::GUI is "best" GUI module/method since it's the only one that I have experience with. However, if you do decide to use it, I'd definitely recommend getting the GUI Loft. Just keep in mind that the GUI Loft hasn't been updated in a long time and is using an older Win32::GUI module than what is currently available, which means that all of its options on objects don't necessarily match up with the current Win32::GUI module.

I've been meaning to take a look into learning Tk so that I can create more cross-platform GUIs, but haven't gotten around to doing it yet.