%{ expr } is your friend: 

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

[download]
Paul Fenwick
Perl Training Australia

In reply to Re: using keys on hash of hash by pjf
in thread using keys on hash of hash by alecclews

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