title: What's the difference between `use base` and @ISA in Perl?
body: <p>I want to make a singleton class which extends DBI. should I be doing something like this:</p>
  
  <pre><code>use base 'Class::Singleton';
  our @ISA = ('DBI');</code></pre>
  
  <p>or this:</p>
  
  <pre><code>our @ISA = ('Class::Singleton', 'DBI');</code></pre>
  
  <p>or something else?</p>
  
  <p>Not really sure what the difference between 'use base' and 'isa' is.</p>