my %a = map { $a{$_} => 1 unless undef, 0..5 } 0..11;

##</code><code>##

my %a = map { 1 unless undef, 0..5 } 0..11;

##</code><code>##

use strict;
use warnings; 

use Data::Dumper qw/Dumper/;
my %a;
#%a = map { $a{$_} => 1 unless undef, 0..5 } 0..11;
#%a = map { $a{$_} , 1 unless undef, 0..5 } 0..11;
%a = map { 1 unless undef, 0..5 } 0..11;
print Dumper \%a;

##</code><code>##

 
Use of uninitialized value in range (or flip) at C:\gash.pl line 10.
Use of uninitialized value in range (or flop) at C:\gash.pl line 10.
Use of uninitialized value in range (or flop) at C:\gash.pl line 10.
Use of uninitialized value in range (or flop) at C:\gash.pl line 10.
Use of uninitialized value in range (or flop) at C:\gash.pl line 10.
Use of uninitialized value in range (or flop) at C:\gash.pl line 10.
Use of uninitialized value in range (or flop) at C:\gash.pl line 10.
Use of uninitialized value in range (or flop) at C:\gash.pl line 10.
Use of uninitialized value in range (or flop) at C:\gash.pl line 10.
Use of uninitialized value in range (or flop) at C:\gash.pl line 10.
Use of uninitialized value in range (or flop) at C:\gash.pl line 10.
Use of uninitialized value in range (or flop) at C:\gash.pl line 10.
Use of uninitialized value in range (or flop) at C:\gash.pl line 10.
$VAR1 = {
          '11' => 12,
          '1' => 2,
          '3' => 4,
          '7' => 8,
          '9' => 10,
          '5' => 6
        };