use strict;
use warnings;
use Data::Dumper;
use Scalar::Util qw(reftype);
my $hashvar = {
               emp => {},
               hemp => {
                        splay => {},
                        hay   => {
                                  go => 1,
                                  ho => {},
                                  },
                        tay   => [],
                        may   => [ 'way' ],
                       },
               };

sub clean {
    my $ref = shift;
    return $ref unless ref $ref;

    if (reftype($ref) eq 'HASH'){
        my %result;
        for (keys %$ref){
            my $tmp = clean($ref->{$_});
            $result{$_} = $tmp if (defined $tmp);
        }
        if (keys %result){
            return \%result;
        } else {
            return;
        }
    }
    elsif (reftype($ref) eq 'ARRAY'){
        return @$ref ? $ref : undef;
    }

}

print Dumper($hashvar, clean($hashvar));
__END__
$VAR1 = {
          'hemp' => {
                      'may' => [
                                 'way'
                               ],
                      'tay' => [],
                      'hay' => {
                                 'ho' => {},
                                 'go' => 1
                               },
                      'splay' => {}
                    },
          'emp' => {}
        };
$VAR2 = {
          'hemp' => {
                      'may' => $VAR1->{'hemp'}{'may'},
                      'hay' => {
                                 'go' => 1
                               }
                    }
        };