Well, did you try setting the ABSOLUTE and/or RELATIVE options, as suggested in the error messages that you quoted?

  my $template = Template->new({
      INCLUDE_PATH => '/templates/includes',
      PRE_PROCESS  => 'config',
      ABSOLUTE     => 1,  # (may want to pick one or the other
      RELATIVE     => 1,  #  instead of using both)
  });
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