[Help]How can I add some char before a block?

[陈方荣]

Hi all，
            How can I add some char before a block?
            Just like C++ comment.
            
            Before：
            Comment line1
            Comment line2
            Comment line3
            Comment line4

            After：
            //Comment line1
            //Comment line2
            //Comment line3
            //Comment line4
            
Thanks.

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Best regards
chenfangrong