I had exactly the same problem.
I solved it like this:
use strict;
use warnings;

use WWW::Mechanize;
use HTTP::Cookies;
use Data::Dumper;

my $url = 'http://search.cpan.org';
my $searchstring = 'mechanize';

my $mech_obj = WWW::Mechanize->new();

$mech_obj->get( $url );

if( not $mech_obj->success() )
{
    print "Could not retrieve page:\n";
    print $mech_obj->content();
    die;
}

print "all forms:\n", Dumper( [ $mech_obj->forms ] );

$mech->submit_form(
        form_number => 1,
        fields      => {
            query   => $searchstring,
        }
    );


print "content:\n", $mech_obj->content();

[download]
"We all agree on the necessity of compromise. We just can't agree on when it's necessary to compromise." - Larry Wall.

In reply to Re: "Unexpected field value" error with WWW::Mechanize by jbrugger
in thread "Unexpected field value" error with WWW::Mechanize by bobf

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