use IO::Pty;
use IO::Handle;

open(REAL_STDOUT,">&STDOUT");
my $pty = new IO::Pty;
my $slave  = $pty->slave;
STDOUT->fdopen($slave,'w') || die $!;
$pty->fdopen(\*REAL_STDOUT,'w') || die $!;
system("echo This is stdout output from an external program");

##</code><code>##

use IO::Handle;
use IO::Pty;
                                                                                                                                                                                                                                                            
sub do_cmd() {
  my $pty = new IO::Pty;
  defined (my $child = fork) or die "Can't fork: $!";
  return $pty if $child;
                                                                                                                              
  POSIX::setsid();
  my $slave  = $pty->slave;
  close($pty);
  STDOUT->fdopen($slave,'>') || die $!;
  STDERR->fdopen(\*STDOUT,'>') || die $!;
  system("echo This is stdout output from an external program");
  exit 0;
}                                                                                                                              

my $fh = do_cmd();
while(<$fh>) { print; }