Net::SSLeay::CTX_set_tlsext_servername_callback($ctx, sub {
                    my $ssl = shift;
                    my $h = Net::SSLeay::get_servername($ssl);

                    if(!defined($h)) {
                        #print STDERR "SSL: No Hostname given during SSL setup\n";
                        return;
                    }  
...
                    # ---- THIS SELECTS THE CORRECT BACKEND -----
                    if(defined($self->{config}->{sslconfig}->{ssldomains}->{$h}->{internal_socket})) {
                        # This SSL connection uses a different backend
                        $selectedbackend = $self->{config}->{sslconfig}->{ssldomains}->{$h}->{internal_socket};
                    }   

                    if($h eq $self->{config}->{sslconfig}->{ssldefaultdomain}) {
                        # Already the correct CTX setting, just return
                        return;
                    }   

...
                        # Switch over to the new certificate key and chain
                        $newctx = Net::SSLeay::CTX_new or croak("Can't create new SSL CTX");
                        Net::SSLeay::CTX_set_cipher_list($newctx, $self->{config}->{sslconfig}->{sslciphers});
                        Net::SSLeay::set_cert_and_key($newctx, $self->{config}->{sslconfig}->{ssldomains}->{$h}->{sslcert},
                                                            $self->{config}->{sslconfig}->{ssldomains}->{$h}->{sslkey})
                                or croak("Can't set cert and key file");
                        Net::SSLeay::CTX_use_certificate_chain_file($newctx, $self->{config}->{sslconfig}->{ssldomains}->{$h}->{sslcert});
                        #print STDERR "Cert: ", $self->{config}->{sslconfig}->{ssldomains}->{$h}->{sslcert}, " Key: ", $self->{config}->{sslconfig}->{ssldomains}->{$h}->{sslkey}, "\n";
                        $self->{config}->{sslconfig}->{ssldomains}->{$h}->{ctx} = $newctx;
                    }
                    Net::SSLeay::set_SSL_CTX($ssl, $newctx);
                });
...
            },