| Character | Description |
|---|---|
| \ | escape "special characters" |
| ^ | start of the line |
| $ | end of the line |
| * | zero or more |
| + | one or more |
| ? | zero or one |
| . | matches one character |
| (pattern) | limits scope, and provides grouping |
| x|y | either x or y |
| {n} | exactly n times |
| {n,} | at least n times |
| {n, m} | at least n times but no more than m times |
| [xyz] | any character listed |
| [^xyz] | any character not listed |
| \b | word boundary |
| \B | non-word boundary |
| \d | digit |
| \D | non-digit |
| \f | form-feed character |
| \r | carriage return |
| \n | new-line character |
| \s | whitespace character |
| \S | non-whitespace character |
| \t | tab |
| \v | vertical tab |
| \w | any word character including underscore |
| \W | any non-word character |