This achieves your goal. But it still loops, albeit that the loop is hidden:

%hash1 = qw( a b c d e f ); 
%hash2 = qw( a J e K y z ); 
@sharedKeys = grep defined( $hash2{ $_ } ), keys %hash1; 
@hash1{ @sharedKeys } = @hash2{ @sharedKeys };;

print %hash1;;
e K c d a J
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