Display a GUI window. The window need not have any contents, but should respond to requests to be closed.

use GTK::Simple;
use GTK::Simple::App;
 
my GTK::Simple::App $app .= new(title => 'Simple GTK Window');
 
$app.size-request(250, 100);
 
$app.set-content(
    GTK::Simple::VBox.new(
        my $button = GTK::Simple::Button.new(label => 'Exit'),
    )
);
 
$app.border-width = 40;
 
$button.clicked.tap: { $app.exit }
 
$app.run;