#! /usr/perl/bin

use warnings;
use strict;
use Data::Dumper;

my $abc = {
  one => {
    oneone => 11,
    onetwo => 12,
  },
  two => {
    twoone => 21,
    twotwo => 22,
  }
};

foreach my $key (keys %{$abc}) {
    if ( ref $abc->{$key} eq 'HASH' ) {
      for my $subkey (keys %{$abc->{$key}}){
        printf qq{%s -> %s\n}, $subkey, $abc->{$key}{$subkey};
      }
    }
}
[download]

onetwo -> 12
oneone -> 11
twotwo -> 22
twoone -> 21
[download]