^start of line
.*any character (except for line terminators), repeated any number of times
\(the literal ( (4010 / 508 / 2816)
Group 1((?:RR|RI|PC|PR|PA)R\d{3}){0,1} {0,1}repeats the group contents below at most once:
Non-Capturing Group(?:RR|RI|PC|PR|PA) RRthe literal text RR (case sensitive) RIthe literal text RI (case sensitive) PCthe literal text PC (case sensitive) PRthe literal text PR (case sensitive) PAthe literal text PA (case sensitive) Rthe literal R (8210 / 1228 / 5216) (case sensitive)
\d{3}a digit, repeated exactly 3 times
\)the literal ) (4110 / 518 / 2916)
the literal (3210 / 408 / 2016)
\[the literal [ (9110 / 1338 / 5B16)
Group 2([1-2]\d{7}@\d{6}) 1-2one character from 1 (4910) to 2 (5010)
\d{7}a digit, repeated exactly 7 times
@the literal @ (6410 / 1008 / 4016)
\d{6}a digit, repeated exactly 6 times
\]the literal ] (9310 / 1358 / 5D16)
\.the literal . (4610 / 568 / 2E16)
Group 3(( <<.*>>)|( (?!<<).+)){0,1} {0,1}repeats the group contents below at most once:
.*any character (except for line terminators), repeated any number of times
2nd Alternative( (?!<<).+) the literal (3210 / 408 / 2016)
.+any character (except for line terminators), repeated at least once
$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