Tk::Error: Can't call method "GetNearest" on an undefined value at C:\Perl\hd16.pl line 66.
 main::DropGlobalGroup at C:\Perl\hd16.pl line 66
 Tk::DropSite::Apply at C:/Perl/site/lib/Tk/DropSite.pm line 66
 Tk::DropSite::Drop at C:/Perl/site/lib/Tk/DropSite.pm line 75
 Tk::DragDrop::Drop at C:/Perl/site/lib/Tk/DragDrop.pm line 285
 (command bound to event)