Either you hardcode them in the program, or you read Getopt::Long, which will explain to you how an option is handled if it is given multiple times.

Also, as I now see, there is documentation at the bottom of the file which shows exactly your use case of specifying multiple columns. Maybe you should read that documentation first?

In reply to Re^3: Merge Columns of Multiple files based on Multiple Common Column by Corion
in thread Merge Columns of Multiple files based on Multiple Common Column by deepak2027

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