Edit in JSFiddle

function Cntl2($scope) {
  var exprs = $scope.exprs = [];
  $scope.expr = '3*10|currency';
  $scope.addExp = function(expr) {
     exprs.push(expr);
  };

  $scope.removeExp = function(index) {
    exprs.splice(index, 1);
  };
}

<div ng-app="">
  <div ng-controller="Cntl2" class="expressions">
    Expression:
    <input type='text' ng-model="expr" size="80"/>
    <button ng-click="addExp(expr)">Evaluate</button>
    <ul>
     <li ng-repeat="expr in exprs">
       [ <a href="" ng-click="removeExp($index)">X</a> ]
       <tt>{{expr}}</tt> => <span ng-bind="$parent.$eval(expr)"></span>
      </li>
    </ul>
  </div>
</div>

</style> <!-- Ugly Hack due to jsFiddle issue: http://goo.gl/BUfGZ --> 
<script src="http://ajax.googleapis.com/ajax/libs/angularjs/1.0.2/angular.min.js"></script>
<style>
.ng-invalid { border: 1px solid red; }