The loud-arm row asserted only a non-empty error on "a*" — a
half-ported arm returning any other error text, or another metachar
falling to the literal default, would have passed. Table over one
pattern per deferred arm ('^' leading, so the r_idx==0 skip gate
composes with the loud arm) compared against the exact boundary
text via strings.compare.
Hojun-Cho
64f6cc90f2