my $file_menu = $mb->Cascade(
        -label      => q{~File},
        -tearoff    => 0,
        -menuitems  => [
            [Separator => q{}],
            [Button => q{Exit}, -command => sub { exit }]
        ],
    );

    $file_menu->cget(q{-menu})->configure(
        -borderwidth => 1,
        -activeborderwidth => 1,
    );

##</code><code>##

    #say qq{\$file_menu: $file_menu};
    #my @file_opts = $file_menu->configure();
    #foreach my $opt (@file_opts) {
    #    map { $_ //= q{undef} } @$opt;
    #    say join qq{\t}, @$opt;
    #}
    #say qq{@{[$file_menu->cget(q{-menu})]}};
    #my %file_menu_menu = %{$file_menu->cget(q{-menu})};
    #foreach my $key (keys %file_menu_menu) {
    #    say join q{ : }, $key, $file_menu_menu{$key};
    #}