Support for array slices

Support for array slices would be greatly appreciated. Our developers are thinking of rules with expressions like the following:

ska/low/station073/beamweights[3,7,9] < ska/low/station073/beamweight_defaults[3,7,9]
ska/low/station073/beamweights3[9-15] < ska/low/station073/beamweight_defaults[9-15]
ska/low/station073/beamweights[3,7,9-15,41,176-211] < ska/low/station073/beamweight_defaults[3,7,9-15,41,176-211]