#!/usr/bin/perl
#
use warnings;
use Data::Dumper;

my $h = { 'foo' => 1 };
if(exists($h->{notexist}{baz})){ }
if(defined($h->{notdefined}{baz})){ }

print Dumper($h);

exit 0;

##</code><code>##

$VAR1 = {
          'notexist' => {},
          'foo' => 1,
          'notdefined' => {}
        };