#!/usr/bin/env perl

use strict;
use warnings;

# Also, see Interactive Client with IO::Socket for another
# demonstration at: http://perldoc.perl.org/perlipc.html

pipe( my $p_rdr, my $c_wtr );
pipe( my $c_rdr, my $p_wtr );

autoflush $c_wtr, 1;
autoflush $p_wtr, 1;

my $pid = fork() // die "can't fork: $!";

if ( $pid ) {
   # parent process
   my $reply;
   while ( defined ( $reply = <$p_rdr> ) ) {
      last if ( length $reply == 1 );
      print $p_wtr "Hello, $reply";
   }
   waitpid $pid, 0;
}
else {
   # child process
   my $reply;
   my @names = qw/ Sun Moon Wind Air /;
   for my $name ( @names ) {
      print $c_wtr "$name\n";
      $reply = <$c_rdr>;
      print $reply;
   }
   print $c_wtr "\n";
   exit 0;
}

##</code><code>##

Hello, Sun
Hello, Moon
Hello, Wind
Hello, Air