gistfile1.txt

sub notes { 
  my ($pattern, @scale) = @_; 

  return map { $note < @scale ? $scale[$note] : undef } split //, $pattern;
} 

#...

for my $note (notes($pattern, @scale)) { 
  if (defined $note) {
    $it->n($note) 
  } 
  else { 
    $it->r 
  }
}