| Symbols | Function |
|---|---|
| ^ | Caret - Marks the Start of input. Ex: ^a matches "a" at the start of input. |
| $ | Dollar sign - Marks the end of input. Ex: b$ matches a "b" at the end of input. |
| . | Dot - Matches a single character except newline. |
| * | Asterisk - Matches the preceding character zero or more times. Ex: ^.*$ matches the entire input. |
| ? | Matches the preceding character zero or one time. |
| + | Matches the preceding character one or more times. o+ would match o, ooo, ooo, etc. |
| [] | Square brackets define a character set to match a single character. Ex: [d-f] or [def] both match "d", "e" or "f". |
| [^] | Caret in square brackets - Negation symbol. Ex: [^0-9] matches any non digit character. |
| () | Parentheses - Define a group of characters that is remembered. The expression can be recalled using $num, where num = 1..n. |
| a{n} | Curly brackets - Number (n) of the preceding character to be matched. Ex: a{2,3} matches "aa" or "aaa". |
| – | Signals not to perform an action. |
| ! | Defines negation. |
| | | Logical ‘OR‘ operator. Ex: (a|b|c)a matches "aa" or "ba" or "ca". |
