Using
http://rubular.com I get as far as
(\.)
giving me
all the dots.
There is something like assertions in regular expressions, where you can say "give me this if not followed by that" or "give me this if it comes after that". however, these don't seem to be available on rubular.com. IIRC, assertions look like
(?<...)
or
(?>...)
.
Then I sometimes get the feeling there are different flavors of regular expressions, while I am under the impression there would be a standard: PCRE. This feeling is amplified when I start
redet and see all the different "programs" it can use for matching.
However, with my lack of patience I couldn't find a regular expression that matches all "." in between "__". Maybe someone else will