How to get a union of regex character classes?

@kadin 

To get a union of regex character classes, you can use the square brackets [] to enclose the characters classes you want to combine. For example, if you want to create a regex pattern that matches either uppercase or lowercase vowels, you can use the following regex pattern:

[AEIOUaeiou]

This pattern will match any uppercase or lowercase vowels. You can add more character classes within the square brackets to create a union of multiple character classes.