?matches at most one character from the set below:
+the literal + (4310 / 538 / 2B16)
-the literal - (4510 / 558 / 2D16)
\d{1,3}a Unicode decimal digit, repeated between 1 and 3 times
\.?optionally matches the literal . (4610 / 568 / 2E16)
\d{1}a Unicode decimal digit, repeated exactly 1 time