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");