Let's start with an example that you can take and adapt to fit your comma-separated datafile. Download (use link at bottom of this node) or cut & paste this code & adapt it. Here's an example of parsing a file containing 3 comma-delimited fields:

#!perl -w
use strict;

open(FILE, "< csv_filename") or die "Couldn't open file, $!";

while(<FILE>) {
   chomp;  # Remove the newline
   my ($var1, $var2, $var3) = split /,/;
   print $var1," ",$var2," ",$var3,"\n";
}
exit;
[download]

We can move on to what you want to do next after you get past reading the file & parsing each line successfully.