my $mech = WWW::Mechanize->new();
$mech->get("https://www.site.com/forums/cs/dispatch.cgi/_admin/diskUsageForm");
$mech->submit_form(
  form_name => 'CFO',
  fields => {
    pforumClass => '__all__',
    tforumClass => '__all__',
    uforumClass => '__all__',
  },
);