Here is one example of where ||= is useful... If this regex doesn't match then $license_class is undefined. Instead of some kind of "if" code that does something "if (!defined ...)", this just sets the default case "BAD_CLASS" if that happens.

my $license_class =  
         ($raw_html =~ m|Class:</td><td class="di">(\w+?) |)[0];
    $license_class ||= "BAD_CLASS";
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