...
    my $frame1 = $mw->Frame()->pack(-side => 'top');
    my $frame2 = $mw->Frame()->pack(-side => 'left');
    my $f_tmp  = $mw->Frame()->pack(-side => 'left');
    my $frame3 = $f_tmp->Frame()->pack(-side => 'top');
    my $frame4 = $f_tmp->Frame()->pack(-side => 'top');