Have you expended any effort other than posting your request? What have you tried? Where's your code and how does it fail to satisfy your intent?

Lacking the above, we're not much inclined to provide specific help -- AKA, do your work for you. See On asking for help and -- at PerlMonks FAQ -- among other helpful explanations of the local value system.

But to get you started, this is a classic case where the Perl solution will closely parallel what you'd do if there were no computer and you had to do this job with two pieces of paper and a stubby pencil. So try writing down an exact outline of the steps you'd need to follow. Then think about unique (which, in Perl, tends to equate to 'think hashes'...and then, in Tutorials study up on hashes.