This smells like homework from thousands of miles away.
And if any monk here does the work for you, that would really not be a favor, because you're never gonna learn anything that way.
We most probably won't do your homework for you, but most monks will be happy to help you if you show some effort to try to solve the problem by yourself and encounter some difficulty.
What you have to do seems to be very easy and you should presumably be able to do it by yourself even with a very basic knowledge of the Perl language. So, please, show the code that you've written and tell us what you don't succeed to do or in which respect your code fails to meet your requirement, and we will happily try to help you.