\[the literal [ (9110 / 1338 / 5B16)
.{23}any Unicode character (except for line terminators), repeated exactly 23 times
]the literal ] (9310 / 1358 / 5D16)
?optionally matches the literal (3210 / 408 / 2016)
.{1,8}any Unicode character (except for line terminators), repeated between 1 and 8 times
:the literal : (5810 / 728 / 3A16)
.{1,12}any Unicode character (except for line terminators), repeated between 1 and 12 times
.*any Unicode character (except for line terminators), repeated any number of times
$end of line
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