my $req = HTTP::Request->new(
  'POST', 
  'https://asite.com:443/sub/create_user.cgi',
  HTTP::Headers->new(
    Content_Type   => 'application/x-www-form-urlencoded',
    Content_Length => 33,
  ),
  '<userCreate>John.Doe</userCreate>',
);

##</code><code>##

my $req = POST
  'https://asite.com:443/sub/create_user.cgi',
  Content => '<userCreate>John.Doe</userCreate>',
);