So, I've seen this sort of notation scattered around in various scripts and while I can see it is a form of logical check, the very nature of the characters makes it rather difficult to search for additional information on. (Alas, if only google used regexps.)
Would any of the more experienced monks kindly bestow upon me knowledge of the proper usage of this, or a link to where I can read up more? Or, at least, what the devil it is called?