(?m)applies the following effective flags to the remainder of the pattern: gm m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string
^start of line
\d{1,2}a Unicode decimal digit, repeated between 1 and 2 times
\d{2}a Unicode decimal digit, repeated exactly 2 times
.*?any Unicode character (except for line terminators), repeated any number of times
\ba Unicode word boundary
Group 1(Reactivated|Re-enabling) 1st AlternativeReactivated Reactivatedthe literal text Reactivated (case sensitive) 2nd AlternativeRe-enabling Re-enablingthe literal text Re-enabling (case sensitive) \ba Unicode word boundary
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