I use perl 5.6.1 under Windows because it needs to run in this environment ... I also tried it in perl 5.8.8 but it didn't print the output at all

The important part of code of the application:

use Tk;
require Tk::ExecuteCommand;

$top = MainWindow->new;
$executecommand = $top->ExecuteCommand( -height => 10, -scrollbars => 
+'se', bg => 'white')->pack( -expand => 'yes', -fill => 'both' );
$executecommand->terse_gui;
$executecommand->bell;
$executecommand->update;
$b_savelog = $top->Button(
    -text    => "Start script",
    -width   => 12,
    -command => sub {

        $executecommand->configure( -command => "sleep.pl");
        $executecommand->execute_command;
        }
)->pack( -side => 'right' );

MainLoop;
[download]

and the sleep.pl for testing:

print "Starting...";
sleep 10;
print "end\n";
[download]

...in the real application I start script which finds specified files in filesystem, parses them and then starts some other scripts ... which takes several minutes

I was thinking about using threads, but I know about some problem with Tk and threads. I think a way could be to change somehow the Tk::ExecuteCommand (http://search.cpan.org/~lusol/tkjuke-1.0.6/Tk/ExecuteCommand.pm) - but I don't how yet...