#!/usr/bin/env perl

use strict;
use warnings;
use autodie;

use POSIX qw{mkfifo};
use Time::HiRes qw{usleep};

my $named_pipe = "pm_1085515_$$.fifo";
unlink $named_pipe if -e $named_pipe;

if (fork) {
    my $timeout = 2;
    local $SIG{ALRM} = sub { die "Timed out after $timeout seconds" };
    alarm $timeout;
    usleep 1e3 until -p $named_pipe;
    alarm 0;

    open my $writer, '>', $named_pipe;
    print $writer "$_\n" for qw{B D C A};
    close $writer;
    wait;
    unlink $named_pipe;
}
else {
    open my $sorter, '|-', 'sort';
    mkfifo $named_pipe, 0600;
    open my $reader, '<', $named_pipe;
    print $sorter $_ while <$reader>;
    close $reader;
    close $sorter;
}

##</code><code>##

B
D
C
A

##</code><code>##

A
B
C
D