^start of line
<the literal < (6010 / 748 / 3C16)
Negated Character Class[^>]+ +matches at least one character outside the set below:
>the literal > (6210 / 768 / 3E16)
>the literal > (6210 / 768 / 3E16)
Non-Capturing Group(?:(?!\1).)+ +repeats the group contents below at least once:
\1the text saved by group 1
.any character (except for line terminators)
\1the text saved by group 1
>the literal > (6210 / 768 / 3E16)
$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