Yes, However, if I wanted to find all of the nodes with a specific status and have VC report the total number of devices that are"ON" how does that look in the Regex tool. I will play more with it tonight.
If all you want to know is the total number of devices that are "on" at a given moment -- without knowing which specific devices are on -- then you can query the status of all devices at once looking for the regex pattern:
formatted="(On)"
Each time the pattern in the brackets is captured it counts as 1 match (first match = {Match.1}, second match = {Match.2} etc.).
Therefore {#M} tells you how many devices are on.
Of course, this will only work for devices that report their on/off state in this format.
The regex tool will show you a list of all the matches. It also provides the total number of matches in the label on the left.
It will not tell you the standard VC syntax for different variables, though. You'll need to know that {#M} refers to the total number of matches, or look in your parameter helper window in VC, or review the wiki page that lists all the standard VC variables.