This statement
printf "%10s\t=>%10s\n" x @ky, @ky, @vals;
is first outputting all keys, then all values. Here's an alternative without the intermediate arrays, using the defined or operator // to avoid a warning on an undef value.

#!/usr/bin/env perl
use strict;
use warnings;

my %hash = ("fred"   => "flintstone", "dino" => undef, 
            "barney" => "rubble",    "betty" => "rubble",
           );

printf "%10s\t=>%10s\n", "keys", "values";
for ( keys %hash ) {
    printf "%10s\t=>%10s\n", $_, $hash{$_} // '';
}
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