Non-Capturing Group(?:(?<=\P{L})(?=(?:\p{Lu}\h+){2}\p{Lu})|\G(?!\A)) 1st Alternative(?<=\P{L})(?=(?:\p{Lu}\h+){2}\p{Lu}) Positive Lookbehind(?<=\P{L}) \P{L}characters not matched by \p{L}
Positive Lookahead(?=(?:\p{Lu}\h+){2}\p{Lu}) Non-Capturing Group(?:\p{Lu}\h+){2} {2}repeats the group contents below exactly 2 times:
\p{Lu}an uppercase letter
\h+any horizontal whitespace character, repeated at least once
\p{Lu}an uppercase letter
\Gstart of current search
\p{Lu}an uppercase letter
\Kresets the starting point of the reported match. Any previously consumed characters are no longer included in the final match
\h+any horizontal whitespace character, repeated at least once
Positive Lookahead(?=\p{Lu}(?!\p{L})) \p{Lu}an uppercase letter
Negative Lookahead(?!\p{L}) g modifier: global. Finds all matches instead of stopping after the first