" # What do I do next? "

Read Tutorials starting with "Getting Started with Perl" and continuing thru "Input and Output."

Next, think about what you would need to do to "select the closest relative..." if you weren't using a computer. Write it down, step by step using whatever pseudocode notation you like to deal with any looping that's necessary... and - bingo! - you'll have an outline of the job.

Then try to write some actual code; not merely a hashbang plus comments. That's when we can really help you learn. If you're not here to learn, then go to a jobs site and hire a programmer.