Orbitz tackled a hard technical problem with Common Lisp. I don&#x27;t know if it was the &quot;secret weapon&quot;, but it must have been fairly critical. They needed efficiency.<p><a href="http:&#x2F;&#x2F;www.paulgraham.com&#x2F;carl.html" rel="nofollow">http:&#x2F;&#x2F;www.paulgraham.com&#x2F;carl.html</a>