Ah, now I see the problem. I couldn't create exact test conditions, so simplified script a bit. There were two problems: first, you forgot to set SO_REUSEADDR, second, AnyEvent::HTTP under the hood tried to create second connection to the server with the same source/destination ports, this of course couldn't work (thanks to strace for the help), I fixed it by setting persistent to 1. So here's the script that worked for me, hope it will help:

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

use AnyEvent;
use AnyEvent::HTTP;
use AnyEvent::Socket    qw( tcp_connect );
use Socket;

my @hosts = qw(host1 host2);
my @ports = qw(80);

my $cv = AnyEvent->condvar;

foreach my $port (@ports) {
    foreach my $host (@hosts) {
        print "[*] $host:$port\n";
        $cv->begin;
        check_http(1111, $host);
    }
}

$cv->recv;

sub check_http {
    my ($port_number, $host) = @_;
    my $ret_val;
    $host = 'http://' . $host;

    http_get $host,
        persistent => 1,
        on_prepare => sub {
            my ($fh) = @_;

            setsockopt($fh, SOL_SOCKET, SO_REUSEADDR, 1) or warn "Coul
+dn't set SO_REUSEADDR";
            bind($fh, sockaddr_in($port_number, INADDR_ANY))
                or print "bind: $!\n";

            15
        },
        sub {
            my ($body, $hdr) = @_;

            if ($hdr->{Status} =~ /^2/) {
                print "Seems OK! (:\n";
            } else {
                print "ERROR, $hdr->{Status} $hdr->{Reason}\n";
            }

            print "[X] $host:$port_number\n";
            $cv->end;
        };
}
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