sub subdivide {
    my ($s, $n) = @_ ;
    $s =~ s/\G(.{$n})(?!\Z)/$1\n/g ;
    return $s ;
  } ;

  print subdivide("trivial\n", 12) ;
  print subdivide("Edge 6789012\n", 12) ;
  print subdivide("Over 6789012+Once\n", 12) ;
  print subdivide("Over 6789012+Once Edge 2\n", 12) ;
  print subdivide("Over 6789012+Once6789012+Twice\n", 12) ;