use strict;
use warnings;
use Data::Dumper;

my $data1 = [
        { "shape" => "round", "food" => "apple" },
        { "shape" => "square", "food" => "pear" }
];

my $data2 = [
        { "big" => "cow", "small" => "bunny" },
];

my $combined;

foreach my $r (@{$data1}) {
        $r->{sizes} = $data2;
        push(@{$combined},$r); 
}

print Dumper($combined);

##</code><code>##

$VAR1 = [
          {
            'food' => 'apple',
            'shape' => 'round',
            'sizes' => [
                         {
                           'small' => 'bunny',
                           'big' => 'cow'
                         }
                       ]
          },
          {
            'food' => 'pear',
            'shape' => 'square',
            'sizes' => [
                         {
                           'small' => 'bunny',
                           'big' => 'cow'
                         }
                       ]
          }
        ];