wtf.js

var my_eval = eval;

(function() {
    var x = 5,
        y = 5;
    eval("var x = 6");
    my_eval("var y = 6");
    console.log(x); // 6
    console.log(y); // 5
})();

console.log(y); // 6
//console.log(x); // error

Yeah, looks like calling any alias to the eval function makes any variables created by eval go into the global scope.