$ perl -E 'use Tk; my $mw = MainWindow::->new(); say $mw->Listbox'
Tk::Listbox=HASH(0x8006859e8)

$ perl -E 'use Tk; my $mw = MainWindow::->new(); say $mw->Scrolled("Listbox")'
Tk::Frame=HASH(0x800647820)