> You need the grouping for the or ( | ) to work appropriately - and not just be an or between characters.

Under what circumstances here do alternations need to be surrounded by groupings?

```
> 'abc' =~ /(abc)|(def)/
 => 0
> 'def' =~ /(abc)|(def)/
 => 0
> 'abc' =~ /abc|def/
 => 0
> 'def' =~ /abc|def/
 => 0
```