I could swear I've seen this behavior before, but can't find the post.

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

my $questions = {
    1 => { foo => 'bar' },
    2 => { foo => 'bar' },
    3 => { foo => 'bar' }
};

print "(before):\n",Dumper($questions),"\n";

for (1 .. 4) {
    my $foo = $questions->{$_}{foo} || "daklfjsdalk";
}

print "(after): \n",Dumper($questions), "\n";

[download]
This returns something like: 
(before):
$VAR1 = {
          1 => {
                 'foo' => 'bar'
               },
          2 => {
                 'foo' => 'bar'
               },
          3 => {
                 'foo' => 'bar'
               }
        };

(after): 
$VAR1 = {
          1 => {
                 'foo' => 'bar'
               },
          2 => {
                 'foo' => 'bar'
               },
          3 => {
                 'foo' => 'bar'
               },
          4 => {}
        };
And I'm not sure why, my question is twofold:
1) Is there a good reason why perl creates the reference (4)?
2) Is there a good reason why perl doesn't WARN that I am trying to access a value that doesn't exist? Note that even taking out the || "djkafdkljfa" does not produce a warning

The problem is appearing in a bit of code I am developing, and I can get around it, but this tripped me up while I was working on it (using exists($hashref->{key} to determine execution path).

ps:
Damn, I miss this place, I think it's time to start hanging out here again (especially now that I "do" perl for a living :))

In reply to Looping through a hash reference is creating a key...? by the_slycer

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