?repeats the group contents below at most once:
test_0xthe literal text test_0x (case insensitive) +matches at least one character from the set below:
0-9one character from 0 (4810) to 9 (5710)
a-fone character from a (9710) to f (10210) (case insensitive)
_the literal _ (9510 / 1378 / 5F16)
+matches at least one character from the set below:
a-zone character from a (9710) to z (12210) (case insensitive)
0-9one character from 0 (4810) to 9 (5710)
\s+a Unicode whitespace character, repeated at least once
orthe literal text or (case insensitive) \s+a Unicode whitespace character, repeated at least once