From type/Supply

See Original text in context

method zip-latest(**@s, :&with, :$initial )

Creates a supply that emits combined values as soon as there is a new value seen on any of the supplies. By default, Lists are created, but this can be changed by specifying your own combiner with the :with parameter. The optional :initial parameter can be used to indicate the initial state of the combined values. By default, all supplies have to have at least one value emitted on them before the first combined values is emitted on the resulting supply. The resulting supply is done as soon as any of the given supplies are done. Can also be called as a class method.