#!/usr/bin/perl -w

use strict;
use warnings;

use Data::Dumper;

my @foo = (
  { 'name' => 'rover' },
  { 'name' => 'felix' }
);

# Modify the first hashref in @foo

print Dumper (\@foo);
$foo[0]->{'food'} = 'Scooby Snacks';
print Dumper (\@foo);
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And so you have added a key to one of the hash references in your array.