my $v = {
        h1 => {
                k1 => 1,
                k2 => 2,
        },
        h2 => {
                k1 => 3,
                k2 => 4,
        },
};

my $interest = 'h1';

foreach my $key ( keys %{ $v->{$interest} } ) {
        print "$key has value $v->{$interest}{$key}\n";
}
__END__
k2 has value 2
k1 has value 1