Topic on Help talk:CirrusSearch

: "Do not run a bare insource:/regexp/ search."

There is no clarification what that means, what is the alternative of a bare regexp?? All examples are bare regexp.

It refers to the previous paragraph, i.e. you should define a search domain in addition to the regex search. So all examples are not bare regexes, as the first four use non-regex insource:, and the fifth uses prefix: to limit the search domain on which the regex is tested.