It seems that Google has dropped the tilde (~) synonym operator (http://googlesystem.blogspot.co.uk/2013/06/googles-tilde-operator-no-longer-works.html). Although Google automatically looks for variations on your terms, placing a tilde before a word seemed to look for more variations and related terms. It meant that you didn’t have to think of all the possible permutations of a word. It was also very useful if you wanted Google to run your search exactly as you had typed it in except for one or two words. The Verbatim option tells Google to run your search without dropping terms or looking for synonyms, but sometimes you might want variations on just one of the words. That was easily fixed by placing a tilde before the word. Now we are left with the OR command, which is unreliable at the best of times.
I must admit I didn’t see this one coming. My money was on another option going first.
Many thanks to Aaron Tay (@aarontay) for the alert.
Update: @dmrussell (https://twitter.com/dmrussell) has confirmed via Twitter that it was removed because it wasn’t much used and Google could not justify the cost of maintaining the index and code.