^start of line
Group 1(2[0-4]\d|25[0-5]|1\d\d|\d\d?) 2the literal 2 (5010 / 628 / 3216)
0-4one character from 0 (4810) to 4 (5210)
\da digit
0-5one character from 0 (4810) to 5 (5310)
1the literal 1 (4910 / 618 / 3116)
\da digit
\da digit
\da digit
\d?optionally matches a digit
\.the literal . (4610 / 568 / 2E16)
(?1)calls group 1 as a subroutine
\.the literal . (4610 / 568 / 2E16)
(?1)calls group 1 as a subroutine
\.the literal . (4610 / 568 / 2E16)
(?1)calls group 1 as a subroutine
$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