Non-Capturing Group(?:\w_){3} {3}repeats the group contents below exactly 3 times:
\wany word character
_the literal _ (9510 / 1378 / 5F16)
\d{8}a digit, repeated exactly 8 times
Tthe literal T (8410 / 1248 / 5416) (case sensitive)
\d{4}a digit, repeated exactly 4 times
_the literal _ (9510 / 1378 / 5F16)
\1the text saved by group 1
Tthe literal T (8410 / 1248 / 5416) (case sensitive)
\d{4}a digit, repeated exactly 4 times
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