Turns out the rabbit hole goes deeper. Adverbs appear to not work if slice is structured:
my %a = 'a'..'z';
dd %a{<a c e>, (<g i k>, ('m', ('o')))}:kv; # OUTPUT: ()
%a{<a c e>, (<g i k>, ('m', ('o')))}:delete;
dd +%a.keys; # OUTPUT: 13
Shouldn't it give structured `kv` data back and delete at least some keys?
