\ba Unicode word boundary
Negated Character Class[^:\n]* *matches any number of characters outside the set below:
:the literal : (5810 / 728 / 3A16)
\na line-feed (newline) character (ASCII 10)
:the literal : (5810 / 728 / 3A16)
\s*a Unicode whitespace character, repeated any number of times
Bthe literal B (6610 / 1028 / 4216) (case sensitive)
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