Regular Expression Visualizer...

Here's a nice little web-based regular expression visualizer (IPv4 address matcher example shown at right).

I'd have killed for something this like 15 years or so ago, when I was first learning how to construct regular expressions.  They were so darned hard to read!  What the heck would

      \d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}

mean to any normal person?  Now, after years and years of practice, the symbolic equivalent of this is kind of “built in” to my brain, just as with Java or JavaScript constructs...