ORA-12729: invalid character class in regular expression

I was creating a regular expression using the Regular Expression Workbench for Oracle for checking if an URL was a well formed Oracle Apex URL, when i hit this error:

ORA-12729: invalid character class in regular expression

The error was easily explained: instead of writing [:digit:], i wrote [:digits:].

Here is the complete list of valid character classes:

[:alnum:] All alphanumeric characters
[:alpha:] All alphabetic characters
[:blank:] All blank space characters.
[:cntrl:] All control characters (nonprinting)
[:digit:] All numeric digits
[:graph:] All [:punct:], [:upper:], [:lower:], and [:digit:] characters.
[:lower:] All lowercase alphabetic characters
[:print:] All printable characters
[:punct:] All punctuation characters
[:space:] All space characters (nonprinting)
[:upper:] All uppercase alphabetic characters
[:xdigit:] All valid hexadecimal characters

You can find the Apex URL pattern in the library of available formats, by checking the format radio button.

See message translations for ORA-12729 and search additional resources.

---

ORA-12729: classe caratteri non valida nell'espressione regolare
ORA-12729: clase de carácter no válida en expresión normal
ORA-12729: classe de caràcter no vàlida a l'expressió regular
ORA-12729: classe de caractères non valide dans l'expression régulière
ORA-12729: Ungültige Zeichenklasse in regulärem Ausdruck
ORA-12729: μη αποδεκτή κλάση χαρακτήρων σε τυπική έκφραση
ORA-12729: ugyldig tegnklasse i almindeligt udtryk
ORA-12729: ogiltig teckenklass i reguljärt uttryck
ORA-12729: ugyldig tegnklasse i det regulære uttrykket
ORA-12729: virheellinen merkkiluokka vakiolausekkeessa
ORA-12729: érvénytelen karakterosztály a reguláris kifejezésben
ORA-12729: clasă de caractere nevalidă în expresia logică
ORA-12729: ongeldige tekenklasse in reguliere uitdrukking
ORA-12729: classe de caractere inválida na expressão comum
ORA-12729: classe de caracteres inválida na expressão regular
ORA-12729: недопустимый класс символа в регулярном выражении
ORA-12729: neplatná třída znaků v regulérním výrazu
ORA-12729: neplatná znaková trieda v regulárnom výraze
ORA-12729: niepoprawna klasa znaku w wyrażeniu regularnym
ORA-12729: düzenli ifadede geçersiz karakter sınıfı
ORA-12729: invalid character class in regular expression