| Predefined term | Matches |
| Horizontal tab | |
| Backspace | |
| v | Vertical tab |
| f | Form feed |
| Carriage return | |
| Newline | |
| cA : cZ | Control characters |
| x0000 : xFFFF | Unicode hexadecimal |
| x00 : xFF | ASCII hexadecimal |
| . | Any character, except for newline ( ) |
| d | Any decimal digit; equivalent to [0-9] |
| D | Any character but a decimal digit; equivalent to [^0-9] |
| w | Any alphanumeric character including underscore; equivalent to [A-Za-z0-9_] |
| W | Any character but alphanumeric and underscore characters; equivalent to [^A-Za-z0-9_] |
| s | Any whitespace character (space, tab, form feed, and so on) |
| S | Any character but a whitespace character |
| A word boundary | |
| B | Not a word boundary (inside a word) |