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We present high-resolution crystal spdctroscopy measurements of then = 3 → n = 2 L-shell x-ray transitions of neonlike W64+, which include seven electric-dipole-allowed transitions, two electric quadrupole transitions, and one magnetic quadrupole transition. The resulting wavelength data are compared to recent calculational results, allowing us to clearly distinguish between different theoretical approaches which need to take into account not only substantial electron correlations effects but also radiative contributions, which in case of the transition from the upper level (Is2 2s1/22p63p3/2)J=1 to the closed-shell neonlike ground state exceeds 20 eV. Best agreement is found with calculations utilizing the relativistic multireference MØller-Plesset approach. In addition to the emission from W64+, we observed several inner-shell collisional satellite lines associated with oxygenlike W66+, fluorinelike W65+, sodiomlike W63-, and magnesiumlike W62+, which provide benchmarks for future calculations as well as for recent calcolations using the relativistic many-body perturbation theory. The present measurements also provide accurate rest wavelengths for establishing the instrumental dispersion needed for future measurements of the core plasma motion in the ITER tokamak and show that the candidate W64+ line for such measurements remains well isolated from neighboring collisional satellite lines even when broadened by the expected high temperatures in this device. [ABSTRACT FROM AUTHOR]