Yet another question which shows you really need to read up on LWP and HTTP headers in general. It's all there ;-) But ok, a quick'n'dirty example:

use LWP::UserAgent;

my $ua = LWP::UserAgent->new();
my $req = HTTP::Request->new( GET => $url );

$req->header(REFERER => "http://faked.referer.invalid");
$ua->request($req);
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