code: function cacheList() {
      if (list.match(/^\w+$/)) {
        return '';
      }
      var listVar = Blockly.PHP.variableDB_.getDistinctName(
          'tmp_list', Blockly.Variables.NAME_TYPE);
      var code = listVar + ' = &' + list + ';\n';
      list = listVar;
      return code;
    }
docs: Cache non-trivial values to variables to prevent repeated look-ups. Closure, which accesses and modifies 'list'.