use Gtk2 '-init';
use Gtk2::Helper;
use Glib qw/TRUE FALSE/;
use IO::Handle;

  my $cmd = [perl => -e => '$|++; for my $i (0..4) { $sum+= $i; print 
+"Line $i: sum = $sum\r"; sleep 1;}'];

  my $cb = sub {print "CB: >>" . shift() . "<<\n";};

  open(my $fh, '-|', @$cmd) or die "failed to launch external command:
+ $!";
  $fh->blocking(0);

  $tag = Gtk2::Helper->add_watch($fh->fileno, in => sub {
    if ($fh->eof) {
      print "pipe EOF\n";
      Gtk2::Helper->remove_watch($tag);
      close $fh;
      return;
    }
    while (1) {
      my $buf;
      $fh->sysread($buf, 4095);
      print "READ: >>$buf<<\n";
      last unless $buf;
      for (split(/[\r\n]/, $buf)) {
        $cb->($_);
      }
    }

    # keep watch active
    return TRUE;
  });

Gtk2->main;

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