You get to see a piece of perl code which (condensed) reads: 

my $v;
# ...
$v = $hash{$foo}->{$bar};

# ... some lines later the same location
# has to be retrieved to check for changes
# to the multilevel hash

$ref = [ $foo, $bar ];

my $nv = $hash{$ref};
if ($v eq $nv) {
    ...

[download]

and you are told that this just works. Can it? does it? how so?

<Reveal this spoiler or all in this thread>

In reply to reference as key to hash by shmem

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