use strict;
use warnings;
use Data::Dumper;
$Data::Dumper::Sortkeys = 1;

use constant FOO => 'the FOO key';

my %h1 = ( +FOO  => "the value" , FOO_const => FOO);
my %h2 = ( FOO , "the value",  FOO => "other value");  # comma
my @a  = ( +FOO, FOO);

print(Dumper(\%h1, \%h2, \@a), $h2{+FOO}, "\n");