my $mech = WWW::Mechanize->new();
        print "Accessing $url\n";
        $mech->get($url);
        print "Downloading the file...";
        $mech->click_button (value => "TAB");
        $mech->save_content( $full_path );
        print "Done.\n";

##</code><code>##

Accessing http://spiedigitallibrary.org/ebooks/spies/kbart?isAuthorized=no
Downloading the file...Can't call method "header" on an undefined value at /exlibris/sfx_ver/app/perl-5.10.1/lib/site_perl/5.10.1/WWW/Mechanize.pm line 2381.