#!/usr/bin/perl -w

use strict;
use IO::Handle;
use POSIX qw /mkfifo/;

mkfifo "fifo", 0777 unless (-p "fifo");

pipe (PARENTR, SAPW);
pipe (SAPR, PARENTW);
SAPW->autoflush(1);
PARENTW->autoflush(1);

my $pid = fork;
if ($pid) {
	close PARENTR; close PARENTW;

	while (1) {
		open FIFOR, "fifo";
		my $line = <FIFOR>;
		close FIFOR;
		print SAPW $line;
		close SAPW; # don't want this
		print <SAPR>;
	}
} else {
	close SAPR; close SAPW;

	open STDIN , '<&PARENTR';
	open STDOUT, '>&PARENTW';

	exec "cat";
	die $!;
}