Google (or any server) can detect the client from 'user-agent' header. Default value for LWP::UserAgent is 'libwww-perl/#.##'(refer LWP::UserAgent) It can be changed by setting agent attribute to any valid user-agent string. Here is one example:

my $ua = new LWP::UserAgent;
$ua->agent('Mozilla/5.0');
#$ua->agent('Checkbot/0.4 ');
#$ua->agent('Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1');
#$ua->agent('FireFox 2');
my $req = HTTP::Request->new(GET => $url);
my $res = $ua->request($req);
if ($res->is_success) {
    print $res->content;  # or whatever
}
else {
    die $res->status_line;
}
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