$str = "this\nis my short\nstring\n\n";

$i=0;
for (split /\n/, $str) {
   print(++$i, ": $_\n");
}

print("\n");

$i=0;
for ($str =~ /.*\n|.+/g) {  # Just like <>
   print(++$i, ": $_");
}