constant RANGE = 10_000;
my %hash is Bag = await do for 1..10 {
    start {
        my %h;
        %h{ ^RANGE .pick }++ for ^100_000;
        %h;
    }
}

say "Seen { %hash.values.grep(* > 0).elems } keys";
# Seen 10000 keys
say "Average value (~100 if threadsafe): { %hash.values.sum / %hash.elems }";
# Average value (~100 if threadsafe): 100