Create a well known place where you will store references to the active classes and objects; this can be a package variable, singleton objects, a registry or whatever.

Here's a sketch using a package variable:

  package MyFramework::DBIClass;

  sub setup { 
    $MyFramework::ActiveDBIClass->connect_database
  }
  
  ...
  
  package MyWebApp;

  $MyFramework::ActiveDBIClass = 'MyWebApp::DBIClass';
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