my $agent = WWW::Mechanize->new(max_redirect=>100); 

### First call - authentication
 
$agent->get('http://search.library.nhs.uk/nhs_sse/zengine?');
    
### Second call - run the search query
    $agent->get('http://search.library.nhs.uk/nhs_sse/zengine?VDXaction=ZSearchAdvanced');
    $agent->form_number(2); 
    $agent->set_fields('search_term_row1'=>'science',
                       'attr_type1_row1'=>'4');
    $agent->click();

print $agent->content;