The meltran package computes the Mellin transform of harmonic polylogarithms and the inverse Mellin transform of harmonic sums. It can do this in principle to any level of complexity, but the constants will only be brought to a minimal representation if the weights involved are at most 9. It can be used for a large number of rather complicated definite and indefinite integrals as well.

It is actually part of the harmpol package.