Simple database query simulated with CSV files and hashes

db.pl

#!/usr/bin/perl

use strict;
use warnings;
use 5.010;

my %data;

open my $fh2, '<', 'file2.txt' or die $!;

# Read second file into a hash (for easy access)
while (<$fh2>) {
  chomp;
  my @row = split /,/;
  $data{$row[0]} = $row[2];
}

open my $fh1, '<', 'file1.txt' or die $!;

while (<$fh1>) {
  chomp;
  my @row = split /,/;
  say "$_,", ($data{$row[1]} // 'N.A');
}