Regular expressions are actually wide- spread, with many tools having some kind of implementation. If you have run grep, egrep or searched for a string while browsing a file with the more command, you have created your first regular expressions. That is until Qedit opened regular expressions to MPE users. The syntax of regular expressions is almost like a mini programming language. Simple expressions can be understood very easily.
More complex expressions have to be evaluated carefully to get the exact meaning.
The existing MPE wildcards and Qedit's pattern matching are fairly powerful too. However, one thing they lack is fine granularity. Wildcard characters usually represent a range of characters at a particular position. What if you want to see strings that contain any letter except vowels. You can easily do all of these tasks with regular expressions.