use strict;
use warnings;
use Socket;

$| = 1;

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

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