I'd recommend reading the QandASection: arrays section of Categorized Questions and Answers. It has lots of entries, including:

• How do I completely remove an element from an array?
• How can I display a unique array if it contains some repeated elements
• How to find and remove duplicate elements from an array?

and probably others which you might find applicable to your situation.

You should also check out the FAQ part of the Perl docs, particularly the Arrays section of perlfaq4.