...
            } else {
                threads->create(
                    \&process_one_req, 
                    $browser, $req, $host
                )->detach;
            }
...

sub process_one_req {
    my ($browser, $req, $host) = @_;
    my $remote = new IO::Socket::INET(
        Proto => "tcp", 
        PeerAddr => $host, 
        PeerPort => 80
    );
    if ($remote) {
        print $remote $req;
        my $chunk;
        print $browser $chunk 
             while (sysread($remote, $chunk, 10000));
        close($remote);
        undef($remote);
    } else {
        print $browser RES_400;
    }
    close($browser);
    undef($req);
    undef($host);
    undef($browser);
}

##</code><code>##

Use of uninitialized value in concatenation (.) or string at P:\test\proxy.pl8 line 42.
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