my $reportLink = WWW::Mechanize::Link->new( {
    url  => 'http://www.website.com/report/runreport/30',
    attr => ([
            'fields[xxx.name]' => 'a name',
            'fields[xxx.version]' => '5.34'
            ])
} );

$mech->put($reportLink);

##</code><code>##

my  $reportLink = URI->new('http://www.website.com/report/runreport/30');
    $reportLink->query_form([
        'fields[xxx.name]' => 'a name',
        'fields[xxx.version]' => '5.34'
    ]);

$mech->put($reportLink);