#!/usr/bin/perl
use strict;
use warnings;

use AnyEvent;

while (1) {
        my $cv = AE::cv;
        my (@output, @input);   
        my $input_waiting = AE::cv;
        my $output_waiting = AE::cv;

        my $input_from_stdin = AE::io *STDIN, 0, sub {
                my $input = <STDIN>; # read it
                push(@input, $input);
                $input_waiting->send;
        };

        # what to do when $input_waiting has sent
        $input_waiting->cb( sub {
                push(@output, 'done');
                $output_waiting->send;
        });

        # what to do when $output_waiting has sent
        $output_waiting->cb( sub {
                print shift(@output) ."\n";
                $cv->send;
        });

        # wait for the main condvar
        $cv->recv;

}