First I'd like to thank Marko for his example, which helped me write my first expression based Smart List. I chose this as an example because it seemed interesting and I'm used to regex from programming.
Here's my expression, which also would be entered into a "Custom" rule:
[=regex([Name], /#^[^a-z]#/,0,0)]=1
It's no easier to understand than Marko's probably, but it's got very powerful syntax. The middle part:
[^a-z]
...says, "don't match any characters in the range of a through z. You could type arbitrary characters to match, or to NOT match in this same area. If you wanted a list of only Qs, Rs, and Zs, you could replace that middle bit with:
[q, r, z]
..and it's done!
It's also worth mentioning that you can build very large lists of rules if you want to, using the Import/Export button at the lower left of the window where you enter your rules. You'll have to use the Expression Language Syntax, but as long as you start with an example, you should be able to duplicate it. You could easily have entered your 26 rules (one for each letter) if you *really* had to.
But Marko's expression is WAY better than 26 rules right?!?
Brian.