  We show that high-temperature perturbation theory describes extremely well
the area law of SU(N) spatial 't Hooft loops, or equivalently the tension of
the interface between different Z_N vacua in the deconfined phase. For SU(2),
the disagreement between Monte Carlo data and lattice perturbation theory for
sigma(T)/T^2 is less than 2%, down to temperatures O(10) T_c. For SU(N), N>3,
the ratios of interface tensions, (sigma_k/sigma_1)(T), agree with perturbation
theory, which predicts tiny deviations from the ratio of Casimirs, down to
nearly T_c. In contrast, individual tensions differ markedly from the
perturbative expression. In all cases, the required precision Monte Carlo
measurements are made possible by a simple but powerful modification of the
'snake' algorithm.
