use Data::Dumper;

   my $hash = {} ;

   $hash->{key1} = 'k1' ;
   $hash->{key1}{key2} = 'k2' ;

   print ">> $hash->{key1}\n" ;
   print ">> $hash->{key1}{key2}\n" ;

print Dumper $hash;
print Dumper \%k1;
^Z
>> k1
>> k2
$VAR1 = {
          'key1' => 'k1'
        };
$VAR1 = {
          'key2' => 'k2'
        };