(defun regexp-opt-group (strings &optional paren lax)
"Return a regexp to match a string in the sorted list STRINGS.
If PAREN non-nil, output regexp parentheses around returned regexp.
If LAX non-nil, don't output parentheses if it doesn't require them.
(defun regexp-opt-group (strings &optional paren lax)
"Return a regexp to match a string in the sorted list STRINGS.
If PAREN non-nil, output regexp parentheses around returned regexp.
If LAX non-nil, don't output parentheses if it doesn't require them.