use strict;
use warnings;
use Tk;

my $top = new MainWindow;
$top->Button(
    -text       => 'Cursor',
    -command    =>  sub {
        $top->configure(-cursor => 'watch');
        $top->idletasks();
        sleep 2;
        $top->configure(-cursor => 'arrow');
    },
)->pack();

MainLoop;