use strict;
use warnings;

my %h1=('qwqw' => {'qw' => 'qww','df' => 'dfff'},);

my %hash=(
'AAA' => 'aaa',
'BBB' => 'bbb',
'CCC' => {'A1' => 'a1','B1' => 'b1','C1' => {'A2' => 'a2','B2' => 'b2','C2' => 'c2END'}},
'DDD' => 'ddd',
'EEE' => \%h1,
'FFF' => 'sdsfsds',
);


ddump (\%hash);

sub ddump
{
  my $ref  = shift;
  my $deep = shift||0;
  foreach my $k (sort keys %{$ref})
          {
            if (ref( ${$ref}{$k}))  {print "\t" x $deep."$k =>\n"; &ddump (${$ref}{$k}, ($deep+1))}
            # key and value
            # else {print "\t" x ($deep)."$k => ${$ref}{$k}\n";}
            # or just the key as your need
            else {print "\t" x ($deep)."$k\n";}

          }

}


# OUTPUT
AAA
BBB
CCC =>
	A1
	B1
	C1 =>
		A2
		B2
		C2
DDD
EEE =>
	qwqw =>
		df
		qw
FFF