| Expression | Description | 
| x | The character x. | 
| "x" | An x, even if x is an operator. | 
| \x | An x, even if x is an operator. | 
| [xy] | The character x or y. | 
| [x-z] | The character x, y, or z. | 
| [^x] | Any character but x. | 
| . | Any character but newline. | 
| ^x | An x at the beginning of a line. | 
| x$ | An x at the end of a line. | 
| x? | An optional x. | 
| x* | Zero or more instances of x. | 
| x+ | One or more instance of x. | 
| x\|y | An x or a y. | 
| \(x\) | An x matched as a sub-expression. | 
| x{m,n} | M through n occurrences of x. | 
| \n | A back reference, where n is a digit 0 through 9. | 
| Example | |
| \(.*"."ini\)\|\(.*"."bat\) | Searches for all files that end with ".ini" or ".bat". |