From language/variables

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The = twigil is used to access Pod variables. Every Pod block in the current file can be accessed via a Pod object, such as $=data, $=SYNOPSIS or =UserBlock. That is: a variable with the same name of the desired block and a = twigil.

  =begin code
  =begin Foo
  ...
  =end Foo
 
  #after that, $=Foo gives you all Foo-Pod-blocks
  =end code

You may access the Pod tree which contains all Pod structures as a hierarchical data structure through $=pod.

Note that all those $=someBlockName support the Positional and the Associative roles.