!/usr/bin/perl

use strict;
use warnings;
use Async;

my $workercount = 10;
my @workerqueue;
for my $i (1..$workercount) {
    my $proc = Async->new( sub { sleep($i*3); print "$i\n"; } );
    print "--> enqueue $proc->{PID}\n";
    push @workerqueue, $proc;
}

while (1) {
    sleep(1);
    my @unfinished;
    while (my $proc = shift @workerqueue) {
        if ($proc and $proc->ready) {
            print "--> $proc->{PID} is ready\n";
            if (my $e = $proc->error) {
                print "Something went wrong.  The error was: $e\n";
            }
            undef $proc;
        } else {
            push @unfinished, $proc;
        }
    }
    push @workerqueue, @unfinished;
    ## START refill queue block ##
    my $free = $workercount - @workerqueue;
    for my $i (1..$free) {
        my $proc = Async->new( sub { sleep($i*3); print "$i new\n"; } );
        print "--> enqueue $proc->{PID}\n";
        push @workerqueue, $proc;
    }
    ## END refill queue block ##
    print "mainloop\n";
}