\w matches all alphanumeric Unicode characters, including ones (e.g., 𝕊)
that BQN treats special. This is especially troublesome for variables;
previously, something like

    𝕊i

would have returned

    (Token.Operator, '𝕊'),
    (Token.Error, 'i'),

instead of

    (Token.Operator, '𝕊'),
    (Token.Name.Variable, 'i').

This extends to special sequences like \b, which care about the
difference between \w and \W.

BQN does not actually use * (ASTERISK) anywhere,
but there is a primitive function ⋆ (STAR OPERATOR).