use strict;
use warnings;

use Data::Dumper qw( Dumper );

sub dumper {
   local $Data::Dumper::Useqq = 1;
   local $Data::Dumper::Terse = 1;
   local $Data::Dumper::Indent = 0;
   return Dumper($_[0]);
}

for (
   [ [1], [], {1 => 2, 2 =>{} } ],
   [ undef, [ undef ], { x => undef }, \undef, \\\undef ],
) {
   my $d = $_;
   print(dumper($d), "\n");
   clean($d);
   print(dumper($d), "\n");
   print("\n");
}