This is similar to capture except that it does not store the
value of the group. Best used when you want to combine several parts
together and do not reference or extract the grouped value later.
group(...)shortcuts, R variables, text, or other rex
functions.
capture for grouping with capturing. Perl 5 Extended
Patterns https://perldoc.perl.org/perlre#Extended-Patterns
Other rex:
%or%(),
capture(),
character_class(),
counts,
lookarounds,
not(),
rex(),
shortcuts,
wildcards