Negated Character Class[^\S\n]* *matches any number of characters outside the set below:
\Sany non-whitespace character
\na line-feed (newline) character (ASCII 10)
\/the literal / (4710 / 578 / 2F16)
\/the literal / (4710 / 578 / 2F16)
\s*any whitespace character, repeated any number of times
SHOW_DONE_BLOCK_the literal text SHOW_DONE_BLOCK_ (case insensitive) .*any character (except for line terminators), repeated any number of times
\na line-feed (newline) character (ASCII 10)
g modifier: global. Finds all matches instead of stopping after the first
i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters
m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string