code: function define(name, expr, global){
    utils.assertType(name, 'string', 'name');
    expr = utils.unwrap(expr);
    var scope = this.currentScope;
    if (global && global.toBoolean().isTrue) {
      scope = this.global.scope;
    }
    var node = new nodes.Ident(name.val, expr);
    scope.add(node);
    return nodes.null;
  }
docs: Set a variable `name` on current scope.
  
  @param {String} name
  @param {Expression} expr
  @param {Boolean} [global]
  @api public