$ua = new LWP::UserAgent;
$request = new HTTP::Request('HEAD', "$URLVAL{URL}");
($response) = $ua->request($request);
if ($response->is_success) {
  print "Location:$URLVAL{URL}\n\n"; # quits if destination site redirects using '?' [or encoded equivalent] in its redirection script
}
else {
  # send user to another cgi that displays some 'failed URL' text.
}