I've realised that I need to do the same problem except that the duplicate may be a particular pattern within an element. So therefore all those elements containing that pattern need to be removed.

You may have to explain this further. To find the elements not matching a particular pattern you can use something like:

@without = grep { !/PATTERN/ } @original;
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I'm not sure that addresses the issue you are trying to describe with the phrase "the duplicate may be a particular pattern within an element."

-sauoq
"My two cents aren't worth a dime.";