use Data::Dumper;
{ my %x = (background => 'red');
  print Dumper(\%x), "\n" }
# $VAR1 = { 'background' => 'red' };

{ my %x = (-background => 'red');
  print Dumper(\%x), "\n" }
# $VAR1 = { '-background' => 'red' };

{ my %x = (+background => 'red');
  print Dumper(\%x), "\n" }
# $VAR1 = { 'background' => 'red' };

{ my %x = (+background => 'red',
           +background => 'green');
  print Dumper(\%x), "\n" }
# $VAR1 = { 'background' => 'green' };

{ my %x = (+background => 'red',
           -background => 'green');
  print Dumper(\%x), "\n" }
# $VAR1 = { '-background' => 'green',
            'background' => 'red' };

##</code><code>##

__SIG__
use B;
printf "You are here %08x\n", unpack "L!", unpack "P4", pack
  "L!", B::svref_2object(sub{})->OUTSIDE;