Your question is too vague. What do you mean by "will not work"? Please tell us what you expect it to do, and what it ends up doing.

That being said, the code you show doesn't do much. It opens the clipboard, attempts to get a format name, and closes the clipboard. You don't attempt to print anything or retrieve any information. Personally, when working with Win32::API, I prefer to print the return value of my Call() invocations, and compare it with the expected return value. This way I know where the program is failing. In your specific code, your call to GetClipboardFormatName returns 0 which means that it either failed, or the format is predefined. I suspect the latter.

One more thing, the second argument to GetClipboardFormatName is a pointer to a string. You specify C in your Win32::API::new. I would think that P is better.