$ cat /tmp/t.pl 
#! /usr/bin/perl
# vim:ts=4 sw=4 sts=4 et nu fdc=3:
use strict;
use warnings;
use Data::Dumper;

my $back->{iglu} = 0;

print Dumper( $back );
printf "v%vd\n", $^V;

__END__

$ perl /tmp/t.pl 
$VAR1 = {
          'iglu' => 0
        };
v5.12.2
$ /opt/perl/bin/perl /tmp/t.pl 
$VAR1 = {
          'iglu' => 0
        };
v5.10.1
$