Here's a better version of my program above, combined into one program and with the race condition fixed:

#!perl -w
use Socket;
use IO::Socket;
use Getopt::Std;
use strict;

$| = 1;
my %opts;
getopts("e:", \%opts);

if ($opts{e}) {
  showerrs($opts{e});
}

my $socklisten = IO::Socket::INET->new(LocalPort => 0,
                 Listen   => 2,
                 Reuse   => 1,
                 Proto    => 'tcp')
               or die "Cannot open socket: $!\n";
my ($port, $myaddr) = sockaddr_in(getsockname($socklisten));
print "port = $port\n";

# Here we start the error process
system("start perl $0 -e $port\n");

# should put alarm() timeout around this section
if (my $readport = $socklisten->accept) {
  print "reading from port\n";
  chomp(my $portback = <$readport>);
  print "Connecting to $portback\n";
  close($readport);
  *STDERR = IO::Socket::INET->new(
        Proto     => "tcp",
        PeerAddr  => "localhost:$portback",
        Timeout   => 30,
     )
     or die "cannot create socketremote: $!\n";
}
close($socklisten);
# 

warn "this is a test";
sleep(3);
print "program exiting\n";
die "I died!!!\n";

sub showerrs {
  my $port1 = shift;
  my $socklisten = IO::Socket::INET->new(LocalPort => 0,
                                   Listen   => 2,
                                   Reuse   => 1,
                                   Proto    => 'tcp')
             or die "Cannot open socket: $!\n";

  my ($port, $myaddr) = sockaddr_in(getsockname($socklisten));

  my $out = IO::Socket::INET->new(
        Proto     => "tcp",
        PeerAddr  => "localhost:$port1",
        Timeout   => 30,
     )
     or die "cannot create socketremote: $!\n";
  print $out "$port\n";
  close($out);
  if (my $readport = $socklisten->accept) {
   print while <$readport>;
 }
 print "Program terminated\n";

 # Unless your DOS box is already configured to wait:
 print "Press Enter to exit ..."; $_ = <>;
 exit(0);
}
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