my @found_keys = grep { exists($hash_b{$_}) } keys %hash_a;
my @matched_keys = grep { $hash_a{$_} eq $hash_b{$_} } @found_keys;

if ( @found_keys == keys %hash_a ) {
    # All keys in %hash_a were found.
}

if ( @found_keys == keys %hash_b ) {
    # All keys in %hash_b were found.
}

if ( @found_keys == @matched_keys ) {
    # All keys matched values.
}