That's the Conditional Operator. You'll often see it referred to as the ternary operator (actually, that's what I usually call it). That single statement could be written as:

my $location_array_ref;

if (ref($location_ref) eq 'ARRAY') {
    $location_array_ref = $location_ref;
}
else {
    $location_array_ref = [ $location_ref ];
}
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There's an assumption here that if it's not an arrayref, it will be a hashref. That seemed like a reasonable assumption to me; especially for a short script intended to demonstrate a technique. Furthermore, trying to guess what other data types you might be working with would simply be other assumptions.

The basic syntax for this operator is:

expression1 ? expression2 : expression3
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There's nothing to say how complex any of those expressions might be; in fact, any of them could include another ternary operator.

Putting all that together, here's an example of far more robust code that allows arrayrefs, hashrefs, scalarrefs and non-reference scalar values with anything else generating an error.

foreach my $e (@{$getToysResults->{Toys}{Toy}}) {
    my $location_ref = $e->{ToyLocations}{ToyLocation};
    my $ref_type = ref $location_ref;
    my $location_array_ref
        = $ref_type eq 'ARRAY'  ? $location_ref
        : $ref_type eq 'HASH'   ? [ $location_ref ]
        : $ref_type eq 'SCALAR' ? [ { locationName => $$location_ref }
+ ]
        : $ref_type eq ''       ? [ { locationName => $location_ref } 
+]
        :                         undef;
    die 'Data corrupt' unless defined $location_array_ref;
    
    for my $location_array_hash_ref (@$location_array_ref) {
        print $location_array_hash_ref->{locationName}, "\n";
    }
}
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If you want to play around with this, here's the code I used for my tests and the output. Note that I changed die to warn to see all conditions being exercised in a single run.