sub count_codes {
  my $file = shift;
  open (FILE, "<$file") or die "Oops, perl says $!\n";
  local $/;
  my @array_codes = split /\s+/, <FILE>;
  close FILE;
  foreach $code_key (@array_codes) {
    $codes{$code_key}++;
  } 
  printf "$_\t$codes{$_}\n" for keys %codes;
}

# call sub
count_codes("/path/to/myfile.txt");