class RuboCop::Cop::Style::EndBlock

at_exit { puts ‘Goodbye!’ }
# good
END { puts ‘Goodbye!’ }
# bad
@example
This cop checks for END blocks.

def on_postexe(node)
  add_offense(node.loc.keyword) do |corrector|
    corrector.replace(node.loc.keyword, 'at_exit')
  end
end