^start of line
\[the literal [ (9110 / 1338 / 5B16)
Negated Character Class[^\]]+ +matches at least one character outside the set below:
\]the literal ] (9310 / 1358 / 5D16)
\]the literal ] (9310 / 1358 / 5D16)
\s+any whitespace character, repeated at least once
\[the literal [ (9110 / 1338 / 5B16)
Group firstfieldname(?<firstfieldname>[^\]]+) Negated Character Class[^\]]+ +matches at least one character outside the set below:
\]the literal ] (9310 / 1358 / 5D16)
\]the literal ] (9310 / 1358 / 5D16)
\s+any whitespace character, repeated at least once
\[the literal [ (9110 / 1338 / 5B16)
Group secondfieldname(?<secondfieldname>[^\]]+) Negated Character Class[^\]]+ +matches at least one character outside the set below:
\]the literal ] (9310 / 1358 / 5D16)
\]the literal ] (9310 / 1358 / 5D16)
\s+any whitespace character, repeated at least once
\[the literal [ (9110 / 1338 / 5B16)
Group thirdfieldname(?<thirdfieldname>[^\]]+) Negated Character Class[^\]]+ +matches at least one character outside the set below:
\]the literal ] (9310 / 1358 / 5D16)
\]the literal ] (9310 / 1358 / 5D16)
\s+any whitespace character, repeated at least once
\[the literal [ (9110 / 1338 / 5B16)
Group fourthfieldname(?<fourthfieldname>[^\]]+) Negated Character Class[^\]]+ +matches at least one character outside the set below:
\]the literal ] (9310 / 1358 / 5D16)
\]the literal ] (9310 / 1358 / 5D16)
\s+any whitespace character, repeated at least once
\[the literal [ (9110 / 1338 / 5B16)
Group username(?<username>[^\]]+) Negated Character Class[^\]]+ +matches at least one character outside the set below:
\]the literal ] (9310 / 1358 / 5D16)
\]the literal ] (9310 / 1358 / 5D16)
\s+any whitespace character, repeated at least once
Group message(?<message>.+) .+any character (except for line terminators), repeated at least once
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