You'll want to mess with the HTTP::Request object that you
pass to UserAgent when making your request.
For example,
[~] $ cat > tmp/referer.pl
require LWP::UserAgent;
my $r = HTTP::Request::->new('GET','http://web2/cgi-bin/printenv');
$r->header("REFERER", "foo");
my $ua = LWP::UserAgent::->new;
print $ua->request($r)->content;
[~] $ perl !$
perl tmp/referer.pl
DOCUMENT_ROOT="/usr/local/apache/htdocs"
GATEWAY_INTERFACE="CGI/1.1"
HTTP_HOST="web2"
HTTP_REFERER="foo"
HTTP_USER_AGENT="libwww-perl/5.48"
PATH="/sbin:/usr/sbin:/bin:/usr/bin:/usr/X11R6/bin"
QUERY_STRING=""
REMOTE_ADDR="192.168.0.1"
REMOTE_PORT="2524"
REQUEST_METHOD="GET"
REQUEST_URI="/cgi-bin/printenv"
[snip remainder of environment]
-dlc |