use Tk;
$top = new MainWindow;
$top->overrideredirect(1);
$top->geometry("100x50+20+20");
$top->Message(-text => "Hello, world!")->place(-x => 0, -y => 0, -relwidth => 1, -relheight => 1);
$top->Button(-text => "x", -padx => 0, -pady => 0, -borderwidth => 0, -command => sub { $top->destroy })->place(-relx => 1, -y => 0, -anchor => "ne");
MainLoop;