$bitmap =~ s{
  (1 (?: ,1 )* )  # match 1 or 1,1 or 1,1,1,...
  |
  ,? (0 (?: ,0 )* )  # match 0 or 0,0 or 0,0,0,...
}{
  # evil tr/// bug with $<DIGITS>
  my ($one, $zero) = ($1, $2);
  ++$i;
  
  if ($zero) { $i += $zero =~ tr/,//; ""; } 
  else {
    if (my $c = $one =~ tr/,//) { "$i-" . ($i += $c) }
    else { $i }
  }
}xge;