(?s)applies the following effective flags to the remainder of the pattern: gis s modifier: single line. Allows a dot to match line terminators
\[the literal [ (9110 / 1338 / 5B16)
.+?any character, repeated at least once
\r?optionally matches a carriage return (ASCII 13)
\na line-feed (newline) character (ASCII 10)
\]the literal ] (9310 / 1358 / 5D16)
g modifier: global. Finds all matches instead of stopping after the first
i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters