<p>Here's a basic regex technique that I've never managed to remember. Let's say I'm using a fairly generic regex implementation (e.g., grep or grep -E). If I were to do a list of files and match any that end in either <code>.sty</code> or <code>.cls</code>, how would I do that?</p>

```
```
egrep "\.sty$|\.cls$"
```
```