#!/usr/bin/perl

use strict;
use warnings;
use Tie::File;

my $filename = 'data.txt';
tie(my @array, 'Tie::File', $filename) or die "Could not open $filename for reading";

my $total_lines = 0;
for (@array) {
  chomp;
  $total_lines += $_;
}
printf "There are %d lines in %s\n", $total_lines, $filename;