^start of line
\h*any horizontal whitespace character, repeated any number of times
\Sany non-whitespace character
.*any character (except for line terminators), repeated any number of times
Positive Lookahead(?=\R+/{24}) \R+a newline sequence, repeated at least once
/{24}the literal / (4710 / 578 / 2F16) , repeated exactly 24 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