in reply to How to use the BalloonInfo of Tk::Widget.pm
As has been pointed out earlier, it is an undocumented helper routine used internally primarily in the Balloon.pm module. Since it is undocumented, you really shouldn't use it since there is no guarantee that it won't change. But really, it's a pretty simple routine, you should be able to figure out and/or replicate the functionality easily just by reading the code.
The primary use seems to be to check the attached -statusmsg and -ballonmsg options (documented in Tk::Balloon under Methods: attach) of the balloon under the pointer and return the first defined value if there is one... though there is nothing preventing you from using it to find the first defined value in any list of the widgets' options, I suppose.