\w+a Unicode word character, repeated at least once
:the literal : (5810 / 728 / 3A16)
\s*a Unicode whitespace character, repeated any number of times
.*?any Unicode character (except for line terminators), repeated any number of times
Positive Lookahead(?=$|]|\s*\w+:(?:\w|\s)) ]the literal ] (9310 / 1358 / 5D16)
3rd Alternative\s*\w+:(?:\w|\s) \s*a Unicode whitespace character, repeated any number of times
\w+a Unicode word character, repeated at least once
:the literal : (5810 / 728 / 3A16)
Non-Capturing Group(?:\w|\s) \wa Unicode word character
\sa Unicode whitespace character
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