I suppose it should have been obvious, but I was still delightfully surprised when Clinton Ebadi came up with these lines on IRC this morning:

ecmascript@(guile-user)> var callcc = this['call/cc']; ecmascript@(guile-user)> var k = false; ecmascript@(guile-user)> 1 + callcc (function (kont) { k = kont; return 0; }); 1 ecmascript@(guile-user)> k (2); 3

42 good times indeed!