sub smart_sort
{
  my @a = lc($a) =~ /(\d+|[a-z]+)/ig; # better split on fields
  my @b = lc($b) =~ /(\d+|[a-z]+)/ig;

  for my $i ( 0..(@a < @b ? $#a : $#b) )
  {
    # try numbers first
    if ( $a[$i] =~ $NUMBER_ONLY_REGEX 
     and $b[$i] =~ $NUMBER_ONLY_REGEX
     and $a[$i] <=> $b[$i] )
    {
      return $a[$i] <=> $b[$i];
    }
    
    # fallback to string compare
    if( $a[$i] cmp $b[$i] )        # no "elsif"
    {
      return $a[$i] cmp $b[$i];
    }
  }
  
  # can't decide by fields, decide by whole string
  return $a cmp $b;
}