Advanced practice on regexp

Hi there,
 
I've just read the great "30 Minute Regex Tutorial", by Jim Hollenhorst. A brilliant piece of writing. Congratulations, Jim. Expresso is also a really superb tool.
 
I would need to go deeper into the advanced aspects of regexp, such as the examples in Table 6 (Table 6. Everything we left out.) in that tutorial.
 
I would like to hear some suggestions about what way I can go. Thanks a lot!
 
Cheers, Manuel