I'd write the perl 6 version slightly differently:

my %hash;
%hash<A><A> = 1;
%hash<A><B> = 2;
%hash<B><A> = 4;
%hash<B><B> = 8;
   
for %hash<B>.kv -> $key, $value {
    say "$key - $value"
}
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It's a minor thing but using angle-brackets-as-quote-word for hash subscripts will be quite common I think once perl6 hits the streets.