Les fonctions pour les chaînes de caractères

• unquote($string) - Removes quotes from a string.
• quote($string) - Adds quotes to a string.
• str-length($string) - Returns the number of characters in a string.
• str-insert($string, $insert, $index) - Inserts $insert into $string at $index.
• str-index($string, $substring) - Returns the index of the first occurrence of $substring in $string.
• str-slice($string, $start-at, [$end-at]) - Extracts a substring from $string.
• to-upper-case($string) - Converts a string to upper case.
• to-lower-case($string) - Converts a string to lower case.