$grammar = <<'__END_OF_GRAMMAR__';

   {
      use strict;
      use warnings;
      $skip = qr/[ \t]*/;
   }

   # Returns a ref to an array of lines.
   parse : line(s?) /$/     { $item[1] }

   # Returns a ref to an array of atoms and lists.
   line  : term(s?) /\n/    { $item[1] }

   # Returns an atom or a list.
   # An atom looks like: [ atom => "text" ]
   # A list is a ref to an array of atoms and/or lists.
   term  : '{' term(s?) '}' { [ list  => $item[2] ] }
         | /[^{} \t\n]+/    { [ atom  => $item[1] ] }

__END_OF_GRAMMAR__