sub get_reserved {
  my $bits_ref = shift;
  my @bits = @{$bits_ref};
  
  my @digits = map {
    chomp;
    if ( m/(\d+):(\d+)/) {
      ($1 > $2) ? ($2 .. $1) : ($1 .. $2);
    }
    else {
      $_;
    } 
  } @bits;

  my @reg32set = map {0} 0 .. 31;
  my @index;
  
  if (@digits ne '') {
    map {$reg32set[$_] = 1;} @digits;
    @index = grep {if ($reg32set[$_] == 0) {$_;}} 0..31;
  }
  else {
    undef @index;
  }
}