#!/usr/bin/perl

use strict;
use warnings;

use constant CONST1=>10;
use constant CONST2=>12;

my %var=(
CONST1=>'test1',
CONST2=>'test2',
);

print $var{CONST1}."\n";
print $var{10}."\n";

##</code><code>##

bash-2.05b$ perl test.pl
test1
Use of uninitialized value in concatenation (.) or string at test.pl line 13.