A canonical Van Vleck quasidegenerate perturbation theory that uses trigonometric transformed generators of the wave operator is presented. The equations for the first-order corrections to the wave operator generator are similar to those used in the stable Jacobi matrix diagonalization algorithm. Use of the trigonometric transformed variables can be seen to eliminate numerical instabilities due to zero-order quasidegeneracy. The separate question of orbital energies for use with the Moller-Plesset partitioned form of this quasidegenerate perturbation theory is also addressed. Results of calculations, through second order, for electron correlation energy in benchmark molecules are presented (i.e., DZ H2O, 6-31G NH2, DZP CH2, (DZ+)P F-2, DZP O-2). Remarkably high accuracy is observed already in the second-order implementation.