Variable: org-tag--group-optional-re
org-tag--group-optional-re is a variable defined in org.el.gz.
Value
"\\(?:[ ]+\\(:\\([[:alnum:]_@#%:]+\\):\\)\\)?[ ]*$"
Documentation
Regexp matching an optional tag group at the end of a line.
Regexp includes leading and optional trailing spaces. If a tag group is present, group 1 is the full tag group (with colons), group 2 is the tag content (without colons).
Source Code
;; Defined in /usr/src/emacs/lisp/org/org.el.gz
(defconst org-tag--group-optional-re
(concat "\\(?:[ \t]+" org-tag--group-enclosed-re "\\)?[ \t]*$")
"Regexp matching an optional tag group at the end of a line.
Regexp includes leading and optional trailing spaces. If a tag group
is present, group 1 is the full tag group (with colons), group 2 is
the tag content (without colons).")