^start of line
Non-Capturing Group(?:.*\b)? ?repeats the group contents below at most once:
.*any character (except for line terminators), repeated any number of times
\ban ASCII word boundary
\w+any word character, repeated at least once
\h*any horizontal whitespace character, repeated any number of times
\ban ASCII word boundary
2the literal 2 (5010 / 628 / 3216)
\ban ASCII word boundary
.*any character (except for line terminators), repeated any number of times
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