my $topframe = $mainWindow->Frame;
$topframe->pack(-expand => 'x', -fill => 1);

my $leftframe = $topframe->Frame;
$leftframe->pack(-side => 'left', -expand => 'x', -fill =>1);
my $rightframe = $topframe->Frame;
$rightframe->pack(-side => 'left', -expand => 'x', -fill =>1);