use IO::Handle;
use IO::Select;

use strict;
use warnings;

$| ++;

pipe(PARENT_RDR, CHILD_WTR);
if (fork()) {
	if (fork()) {
		close CHILD_WTR;
		while (my $line = <PARENT_RDR>) {
			print "parent got $line";
		}
	} else {
		close PARENT_RDR;
		for (100..110) {
			print CHILD_WTR "$_\n";
		}
	}
} else {
	close PARENT_RDR;
	for (0..10) {
		print CHILD_WTR "$_\n";
	}
}

##</code><code>##

parent got 0
parent got 1
parent got 2
parent got 3
parent got 4
parent got 5
parent got 6
parent got 7
parent got 8
parent got 9
parent got 10
parent got 100
parent got 101
parent got 102
parent got 103
parent got 104
parent got 105
parent got 106
parent got 107
parent got 108
parent got 109
parent got 110

##</code><code>##

use IO::Handle;

use strict;
use warnings;

$| ++;

pipe(GRANDPARENT_RDR, PARENT_WTR);

if (fork()) {
	close PARENT_WTR;
	while (my $line = <GRANDPARENT_RDR>) {
		print "grand parent got $line";
	}
} else {
	close GRANDPARENT_RDR;
	pipe(PARENT_RDR, CHILD_WTR);
	if (fork()) {
		close CHILD_WTR;
		while (my $line = <PARENT_RDR>) {
			print "parent got $line";
			print PARENT_WTR $line;
		}
	} else {
		close PARENT_RDR;
		for (0..10) {
			print CHILD_WTR "$_\n";
		}
	}
}

##</code><code>##

parent got 0
parent got 1
parent got 2
parent got 3
parent got 4
parent got 5
parent got 6
parent got 7
parent got 8
parent got 9
parent got 10
grand parent got 0
grand parent got 1
grand parent got 2
grand parent got 3
grand parent got 4
grand parent got 5
grand parent got 6
grand parent got 7
grand parent got 8
grand parent got 9
grand parent got 10