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,
    );