It doesn't do anything. It's included simply to make adding new items to the list or hash more convenient. Without the extra comma, adding something to the list requires going back to the "clean => ...." line and adding a comma, and then adding the new thing on the next line. It's easy to forget to add the comma, so people often use extra commas after the last item so they won't have to worry about it if they think they'll need to add or remove options from the list often.

In reply to Re: strange comma by tcurtis
in thread strange comma by xiaoyafeng

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