^start of line
\(?optionally matches the literal ( (4010 / 508 / 2816)
\+?optionally matches the literal + (4310 / 538 / 2B16)
Non-Capturing Group(?:\d{3})? ?repeats the group contents below at most once:
\d{3}a digit, repeated exactly 3 times
\)?optionally matches the literal ) (4110 / 518 / 2916)
?matches at most one character from the set below:
-the literal - (4510 / 558 / 2D16)
.the literal . (4610 / 568 / 2E16)
the literal (3210 / 408 / 2016)
Negative Lookahead(?!(\d)\1{9}) \1{9}the text saved by group 1, repeated exactly 9 times
\d{10}a digit, repeated exactly 10 times
$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