Ths is just atrocious - Perle is attempting to use the courts and libel laws of another country to intimidate and silence a American journalist over something printed in an American publication. It would be one thing if Perle were just a private citizen, but he isn't. He's an official government advisor - specifically the chariman of the Defense Policy Board - and obviously no small player in this administration.
Britain's libel laws suck - their only consolation is that occasionally people who sue under them - such as Jeffrey Archer - get caught perjuring themselves and end up being thrown in jail for a lovely holiday.
Oh, and P.S. - here's the article in question.