The extra backslash blackslash period in the beginning is needed because this...
is a valid name of a file. You want to only remove the extension -- not everything else.
Henry, does it means start with any word character and end with \\. but do not include \\. in result.
Does positive lookahead ?= used for exclusive ending boundary.
Basically yes. A positive lookahead means to look to match it, but it does not count in the result. It is great for looking for boundaries, where the boundary is related to the next match. Or delimiters.