POST $url, [$form_ref], [Header => Value,...]
           This works mostly like GET() with POST as the method,
           but this function also takes a second optional array
           or hash reference parameter ($form_ref).  This argu-
           ment can be used to pass key/value pairs for the form
           content.  By default we will initialize a request
           using the "application/x-www-form-urlencoded" content
           type.  This means that you can emulate a HTML <form>
           POSTing like this:

             POST 'http://www.perl.org/survey.cgi',
                  [ name   => 'Gisle Aas',
                    email  => 'gisle@aas.no',
                    gender => 'M',
                    born   => '1964',
                    perc   => '3%',
                  ];

           This will create a HTTP::Request object that looks
           like this:

             POST http://www.perl.org/survey.cgi
             Content-Length: 66
             Content-Type: application/x-www-form-urlencoded

             name=Gisle%20Aas&email=gisle%40aas.no&gender=M&born=1964&perc=3%25