Use Smart::Comments module for debugging

use Smart::Comments;
 ### Expected: 2 * $prediction
 ###      Got: $result
would prints:
 ### Expected: 42
 ###      Got: 13

如果只是perl表达式，则：
### 2 * $prediction
### $result
would prints:
### 2 * $prediction: 42
### $result: 13

调试完毕后，不需要移除这些注释行，只需要注释掉第一行即可。

另外这个模块还提供了processing bar功能：
#### Debugging here...

    for (@values) {         ### Progress: 0...  100
        do_stuff();
    }

Click the url below for more details:
http://search.cpan.org/dist/Smart-Comments-v1.0.3/lib/Smart/Comments.pm