Negative Lookbehind(?<!\S) \Sany character that is not Unicode whitespace
\d+a Unicode decimal digit, repeated at least once
Non-Capturing Group(?:/\d+)? ?repeats the group contents below at most once:
/the literal / (4710 / 578 / 2F16)
\d+a Unicode decimal digit, repeated at least once
\sa Unicode whitespace character
A-Zone character from A (6510) to Z (9010) (case sensitive)
a-zone character from a (9710) to z (12210) (case sensitive)
.*?any Unicode character (except for line terminators), repeated any number of times
Positive Lookahead(?=\s+\d+\b|$) \s+a Unicode whitespace character, repeated at least once
\d+a Unicode decimal digit, repeated at least once
\ba Unicode 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