^start of string
.*any Unicode character, repeated any number of times
\s*a Unicode whitespace character, repeated any number of times
%the literal % (3710 / 458 / 2516)
.*?any Unicode character, repeated any number of times
\r?optionally matches a carriage return (ASCII 13)
\na line-feed (newline) character (ASCII 10)
s modifier: single line. Allows a dot to match line terminators
i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters