^start of line
.*?any character (except for line terminators), repeated any number of times
\h+any horizontal whitespace character, repeated at least once
\Kresets the starting point of the reported match. Any previously consumed characters are no longer included in the final match
+matches at least one character from the set below:
А-Яone character from А (104010) to Я (107110) (case sensitive)
а-яone character from а (107210) to я (110310) (case sensitive)
Positive Lookahead(?=\h+[А-Яа-я]+$) \h+any horizontal whitespace character, repeated at least once
+matches at least one character from the set below:
А-Яone character from А (104010) to Я (107110) (case sensitive)
а-яone character from а (107210) to я (110310) (case sensitive)
$end of line
m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string
g modifier: global. Finds all matches instead of stopping after the first