That part is primitive and based on the user-agent string that LWP sends in its headers identifying iteself as lwp/some_version. You will get the expected response if you masquarade as IE but of course that is immoral, possibly illegal but as far as I know not fattening.

use LWP::UserAgent;
use Data::Dumper;
my $ua = LWP::UserAgent->new;
$ua->agent('Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; compaq)
+');
my $request = HTTP::Request->new( 'GET', 'http://www.google.com/search
+?q=google+api' );
my $response = $ua->request( $request );
print Dumper $response;
[download]

If you are interested in the throttling see Throttling Apache or mod_throttle or Google for terms like 'throttle bandwidth shaping'