#!/usr/bin/perl
    use strict;
    use warnings;
    use diagnostics;
    use Data::Dumper;


    open (F, "input.csv");
    my @lines=<F>;
    close(F);

    open (F1,'>>output.csv');

    define my variables;

    for (my $i=1; $i<@lines; $i++){

    read in one line of data;
    do stuff;

    write to file;
    }

    close(F1);