Have you looked at the pod documentation for that module?

% perldoc HTTP::Request::Common
[download]

It has an example that appears to do exactly what you want:

POST 'http://www.perl.org/survey.cgi',
                  Content_Type => 'form-data',
                  Content      => [ name  => 'Gisle Aas',
                                    email => 'gisle@aas.no',
                                    gender => 'M',
                                    born   => '1964',
                                    init   => ["$ENV{HOME}/.profile"],
                                  ]
[download]

-Blake