How about we do it on the page instead of in the .htaccess....
Remove the redirect from the .htaccess file and just add this to the top of the page itself.
<?php
if (isset($_GET['perm']) && $_GET['perm'] == "fibre-optic-curing-systems") {
header("HTTP/1.1 301 Moved Permanently");
header("Location: http://www.domain.com/product/field--in-situ-curing-system");
}
?>