The Tor Browser / file revision

 // frame.eval works in the enterFrame hook.

 // It triggers the enterFrame hook again, recursively. (!)

 var g = newGlobal();

 g.a = ".";

 var dbg = Debugger(g);

 var nestCount = 0, N = 9;

 var log = "";

 dbg.onEnterFrame = function (frame) {

     assertEq(frame.type, "eval");

     if (nestCount < N) {

         log += '(';

         nestCount++;

         var a = frame.eval("a").return;

         log += a;

         nestCount--;

         log += ')';

     }

 };

 assertEq(g.eval("a"), ".");

 assertEq(log, Array(N + 1).join("(") + Array(N + 1).join(".)"));