Those are characters used in the Match Pattern function to search for characters. If you crack open the manual (Help->Search the LabVIEW Help menu item) and switch to the Index tab, and enter "Match Pattern" in the textbox you can click on the "special characters" topic which explains all those characters.
EDIT: Sorry for the double-answer. Posted at the same time as altenbach responded.
Message Edited by smercurio_fc on 10-04-2007 09:13 AM