for my $file (sort grep -f, readdir $dh)

##</code><code>##

for my $file (sort @files)

##</code><code>##

use constant TWO => 2;

##</code><code>##

use constant NUM_EYES => 2;

##</code><code>##

  my $num = 1;
  if (exists $extensions{$key}) {
    $extensions{$key} += $num;
  }
  else {
    $extensions{$key} = $num;
  }

##</code><code>##

  if (defined $extensions{$key}) {
    $extensions{$key} += 1;
  }
  else {
    $extensions{$key} = 1;
  }

##</code><code>##

  ++$extensions{$key};