Compare also for the digraph "nn", with the tilde as a superscript . The vowel variants with a tilde are nasalized. Hindko dialects possess phonemic nasal vowels (here marked with a tilde above the vowel&colon; ). This diacritic is often mistaken for a tilde in modern reproductions of early Vietnamese writing. They may be used along with the tilde that marks nasal vowels. In other cases, nasal vowels are marked with a tilde. The symbol looks like a letter U with a superimposed tilde. It is a version by Tilde SIA with Cyrillic support. Acute, grave, and tilde diacritics are used to indicate pitch accents. The tilde (codice 4) is the default repetition separator. The tilde operator was also adopted by Perl. This mimics the Unix shell usage of the tilde. The tilde can indicate approximate equality in a variety of ways. Nasalization is marked with a tilde. Later a variant similar to the tilde (~) was also used.