#!/usr/bin/perl -w
use strict;
use Data::Dumper;


my $hoh  = { 
              'pk1' => {
                          'sk1' => [
                                     'val1',
                                     'val2'
                                   ],
                          'sk2' => {
                                      'tk1' => 'val1 val2 ',
                                      'tk2' => 'val9,val7'
                                   },
                           'sk3' => 'val10 val11',
                            'sk4' => 21
                        },
 
          'pk2' => {},
        }; 
#print Dumper $hoh;


foreach my $k ( keys %{$hoh} ) 
{

    if( $hoh->{$k} ) 
    {
       print "$k\n";
    };
    
}