code: function VarCommand(value, engine) {
          var match = value.match(/^\s*([a-z0-9_]+)\s*=([\s\S]*)$/i);
          if (!match) {
              throw new Error('Invalid ' + this.type + ' syntax: ' + value);
          }
  
          this.name = match[1];
          this.expr = match[2];
          Command.call(this, value, engine);
          this.cloneProps = ['name', 'expr'];
      }
docs: Var命令节点类
  
  @inner
  @constructor
  @param {string} value 命令节点的value
  @param {Engine} engine 引擎实例