#! perl -slw
use strict;
use threads qw[ async ];
use Tk;
use Tk::ProgressBar;
use Tk::ROText;

my $cmd = 'perl -le" print for 1 .. 10; sleep 10; exit 123"';
my $mw = MainWindow->new;

my $pb = $mw->ProgressBar()->pack();

my $txt = $mw->ROText(
    -width => 3,
    -height => 1,
)->pack( -side => 'left' );

my $edit = $mw->Entry(
    -width => 80,
    -textvariable => \$cmd
)->pack( -side => 'left' );

my $btn  = $mw->Button(
    -text => 'Doit',
    -command => sub{
        async{
            system $cmd;
            $txt->Contents( $? >> 8 );
        };
    }
)->pack( -side => 'left' );

my $progress = 0;
my $repeat = $mw->repeat(
    100 => sub{
        $progress = 0 if ++$progress == 100;
        $pb->value( $progress );
    }
);

MainLoop;