Read Files and Print Total

#!/usr/bin/perl
use strict;
use warnings;
use utf8;
use open qw(:encoding(utf8) :std);
use feature 'say';
my $total = 0;
foreach (glob "${ARGV[0]}/*.dat") {
  open my $in, '<', $_;
  while (<$in>) {
    $total += $_;
  }
  close $in;
}
say $total;