Question

I’m having troubles with a Perl script. I try to store a hash in a hash. The script is trivial:

use Data::Dumper;

my %h1=();
$h1{name}="parent";
my %h2=();
$h2{name}="child";

$h1{nested}=%h2; # store hash h2 in hash h1

print "h2:\n";
print Dumper(%h2); # works
print "h1{nested}:\n";
print Dumper($h1{nested}); # fails

The results:

h2:
$VAR1 = 'name';
$VAR2 = 'child';
h1{nested}:
$VAR1 = '1/8';

Why is the $h1{nested} not dumped as a hash, but as some kind of weird scalar (1/8)?

PS: even if this question sounds trivial – I searched SO but did not find that it was asked before.
PPS: my Perl is v5.10.1 (*) built for x86_64-linux-gnu-thread-multi
(with 53 registered patches, see perl -V for more detail)

Answer 1

You can only store a hashref in a hash:

$h1{nested}=\%h2;

and then you would access %h2‘s name by doing

$h1{nested}->{name}

In your code, %h2 is forced to scalar context, which shows you that “1/8” value, and stores that.