Non-Capturing Group(?:\+?\d{1,2}\s)? ?repeats the group contents below at most once:
\+?optionally matches the literal + (4310 / 538 / 2B16)
\d{1,2}a digit, repeated between 1 and 2 times
\sany whitespace character
\(?optionally matches the literal ( (4010 / 508 / 2816)
\d{3}a digit, repeated exactly 3 times
\)?optionally matches the literal ) (4110 / 518 / 2916)
\sany whitespace character
.the literal . (4610 / 568 / 2E16)
-the literal - (4510 / 558 / 2D16)
\d{3}a digit, repeated exactly 3 times
\sany whitespace character
.the literal . (4610 / 568 / 2E16)
-the literal - (4510 / 558 / 2D16)
\d{3,4}a digit, repeated between 3 and 4 times
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