As usual with perl, TIMTOWTDI (There's More Than One Way To Do It).

The following nodes list the methods above, and many more. Deciding unique elements of an array, How can I extract just the unique elements of an array?, and Return a Unique Array. Pick whichever method best solves the problem at hand.

I found all the above nodes using the search box. I simply used most of the words in the title of your node, plus the key word in your question "unique". My search was simply "unique elements in array". This returned about 50 nodelets. The three above are just three I selected semi-randomly.

Next time, try a search using the important words from your question and see if your question has already been answered. That way you get your answer right away.