The first two keys there evaluate to false, and would cause a problem with the code.

OK - thanks SJ,

I had thought that when Martin said "boolean false values", he literally meant hash values, as opposed to hash keys, which is why I questioned it, but I guess he meant values in the more general sense (i.e. keys in this case).

Actually, I did mean values and not hash keys. Here is an example of how boolean false values would defeat our intent to short-cut at the first match:

my %access = ('foo' => 0, 'bar' => 123);
print $access{'foo'} || $access{'bar'}; # prints 123
[download]

The key 'foo' exists but the zero score makes perl evaluate the second operand, too. With perl version 5.10.0 and up, the defined-or operator can help, as it short-cuts only on undef:

my %access = ('foo' => 0, 'bar' => 123);
print $access{'foo'} // $access{'bar'}; # prints 0
[download]

Older perls don't have this operator, however.