Here's code from my last attempt to get this to work, which I think will probably illuminate whatever it is I'm failing to understand about pseudo-ttys and perl filehandles and whatnot. It attempts to create a pseudo-tty, and then use fdopen to "inject" the pseudo-tty into the path of STDOUT traffic to make STDOUT look like a tty:

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");
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/Edited to add more... Round 2: Some more investigation and now I'm at this solution (stolen from some webpage somewhere and hacked up). This seems to get the output through the pty, but the while/print loop at the bottom never terminates, even though the process writing to the filehandle in question is long gone...

use IO::Handle;
use IO::Pty;
                                                                      
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sub do_cmd() {
  my $pty = new IO::Pty;
  defined (my $child = fork) or die "Can't fork: $!";
  return $pty if $child;
                                                                      
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  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;
}                                                                     
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my $fh = do_cmd();
while(<$fh>) { print; }
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