  The vacuum oscillation solution to the solar neutrino problem predicts
characteristics variations of the observable neutrinos rates, as a result of
the L/E_nu dependence of the nu_e survival probability (L and E_nu being the
neutrino pathlength and energy, respectively). The E_nu-dependence can be
studied through distortions of the recoil electron spectrum in the
SuperKamiokande experiment. The L-dependence can be investigated through a
Fourier analysis of the signal in the SuperKamiokande and Borexino experiments.
We discuss in detail the interplay among such observable variations of the
signal, and show how they can help to test and constrain the vacuum oscillation
solution(s). The analysis includes the 374-day SuperKamiokande data.
