^start of string
\[the literal [ (9110 / 1338 / 5B16)
\d+a digit, repeated at least once
\.the literal . (4610 / 568 / 2E16)
.*?any character, repeated any number of times
\s*any whitespace character, repeated any number of times
\]the literal ] (9310 / 1358 / 5D16)
$end of string, or before its final line terminator
s modifier: single line. Allows a dot to match line terminators