rex(..., env = parent.frame())shortcuts, R variables, text, or other ., capture,
capture_group;
%if_next_is%,
%if_next_isnt%,
%if_prev_is%,
%if_prev_isnt%,
lookarounds; %or%,
or; any_of,
character_class, except,
except_any_of,
except_some_of,
exclude_range, none_of,
one_of, range,
some_of; at_least,
at_most, between,
counts, n,
n_times; group;
maybe, one_or_more,
wildcards, zero_or_more,
zero_or_one; not;
shortcuts