\ban ASCII word boundary
section the literal text section (case sensitive) \d+a digit, repeated at least once
the literal (3210 / 408 / 2016)
Non-Capturing Group(?:(?!\bsection \d+).)*? *?repeats the group contents below any number of times:
Negative Lookahead(?!\bsection \d+) \ban ASCII word boundary
section the literal text section (case sensitive) \d+a digit, repeated at least once
.any character (except for line terminators)
Non-Capturing Group(?:19|20) \d{2}a digit, repeated exactly 2 times
\ban ASCII word boundary
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