| ^ | Beginning of a line | 
| $ | End of a line | 
| . | Any character | 
| Expression? | The expression zero or one times | 
| Expression* | The expression zero or more times | 
| Expression+ | The expression one or more times | 
| Expression{n} | The expression n times | 
| Expression{n,} | The expression at least n times | 
| Expression{n,m} | The expression at least n but no more than m times | 
| Expression1|Expression2 | The expression1 or the expression2 | 
| (Expression) | The expression within the brackets | 
| \1 \2 ... \n | The content of the nth bracket |