- For every array element,
  - Extract the numeric component of the element.
  - If the hash contains a key matching the extracted component,
    - If the hash value is empty,
      - Print whatever
    - Else
      - Print whatever

##</code><code>##

for my $id (@array_code) {
   my ($num) = $id =~ /(\d+)/ or next;
   next if !exists($code_numbers{$num});
   my $code = $code_numbers{$num} || 'IN';
   print("$id $code\n");
}

##</code><code>##

for my $id (@array_code) {
   my ($num) = $id =~ /(\d+)/ or next;
   next if !exists($code_numbers{$num});
   my $code = $code_numbers{$num};
   $code = 'IN' if !length($code);
   print("$id $code\n");
}