>> I've used \x20 to make spaces more visible; also used Extended Mode to separate the subpatterns a bit.
How did you learn all of this stuff ... geez! Extended mode is a new
one to me. All proud to understand \K and now more ...
Triggered with the (?x):
In free-spacing mode, whitespace between regular expression tokens is
ignored. Whitespace includes spaces, tabs and line breaks. Note that
only whitespace between tokens is ignored. E.g. a b c is the same as abc
in free-spacing mode, but \ d and \d are not the same. The former
matches d, while the latter matches a digit. \d is a single regex token
composed of a backslash and a "d". Breaking up the token with a space
gives you an escaped space (which matches a space), and a literal "d".
From RegEx Buddy help.