#!/usr/bin/perl 
use warnings;
use strict;
use IPC::Open3;
use Tk;

$|=1;
my $pid=open3(\*IN,\*OUT,0,'/bin/bash');

my $mw=new MainWindow;
$mw->geometry("600x400");

my $t=$mw->Scrolled('Text',-width => 80,
     -height => 80,
     )->pack;

&refresh;

$mw->fileevent(\*OUT,'readable',\&write_t);

#keep filling the text widget
my $id = Tk::After->new($mw,2000,'repeat',\&refresh);

MainLoop;

sub refresh{
print IN "top b n 1";
print IN "\n";  #absolutely needed and on separate line
}

sub write_t {
  my $str= <OUT>;
  $t->insert("1.0",$str);
#  $t->see("0.0");
}
__END__