not sure what the issue is, but maybe try WWW::Mechanize's submit_form method instead? 
my $mech = WWW::Mechanize->new();
$mech->get("https://www.site.com/forums/cs/dispatch.cgi/_admin/diskUsa
+geForm");
$mech->submit_form(
  form_name => 'CFO',
  fields => {
    pforumClass => '__all__',
    tforumClass => '__all__',
    uforumClass => '__all__',
  },
);

[download]
Also maybe see if the output from mech-dump gives you any extra information ...

And also do a die $mech->content; after the ->get() to make sure it's really the page you expect it is ...

In reply to Re: WWW::Mechanize select from dropdown by davidrw
in thread WWW::Mechanize select from dropdown by camerlengo

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