Hex Editor Neo allows you to define any number of named regular expression classes. Each class is a regular expression with a name assigned to it. A defined class may later be referenced in the regular expression (and in another named class) using the following syntax:
(?$name)
The concept of named classes is so powerful, that it even allows you to define complex recursive grammars. This documentation provides one example of how this feature may be used. See the Expression Demo section for more information.