use strict;
use warnings;
use Socket;
use IO::Handle;

my ($kidfh, $dadfh);
socketpair($kidfh, $dadfh, AF_UNIX, SOCK_STREAM, PF_UNSPEC)
   or die "socketpair: $!";

$kidfh->autoflush(1);
$dadfh->autoflush(1);

if (my $pid = fork) {
  close $dadfh;
  print $kidfh "Parent Pid $$ sendet dies\n";
  chomp(my $line = <$kidfh>);
  print "Parent Pid $$ liest gerade dies: $line\n";
  close $kidfh;
  waitpid($pid,0);
} else {
  close $kidfh;
  chomp(my $line = <$dadfh>);
  print "Child Pid $$ liest gerade dies: $line\n";
  print $dadfh "Child Pid $$ sendet dies\n";
  close $dadfh;
  exit;
}