Non-Capturing Group(?:\bstart:|\G(?!^)) \ban ASCII word boundary
start:the literal text start: (case sensitive) \Gstart of current search
\.?optionally matches the literal . (4610 / 568 / 2E16)
\Kresets the starting point of the reported match. Any previously consumed characters are no longer included in the final match
\d+a digit, repeated at least once
g modifier: global. Finds all matches instead of stopping after the first
m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string