say ('1_3' + 0);
say ('0xd' + 0);
say ('0b1101' + 0);
say ('1.3e1' + 0);
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Literals are irrelevant, the conversion from string to number is what counts, because that's what's more often than not what happens to the matched string, and only the last one actually works.

There's no reason whatsoever not to require \p{Number} for the rare use case of "give me anything that might be a digit to someone".