This is a faq. See perldoc4, near unique. I also find the following entries when googling for perl unique:

• Recipe 4.6. Extracting Unique Elements from a List (in the Perl Cookbook, no link from here)
• How can I extract just the unique elements of an array?

... and some more. I wonder whether you've seen these links and what parts of the solutions presented there you had problems with.