We don't need no stinkin' databases!

incrementer.rb

#!/usr/bin/env ruby
require 'yaml'

puts "How many sections?"
number_of_sections = Integer(gets)

data = YAML.load(DATA)
data['start'] = data['end'] + 1
data['end'] += number_of_sections

File.open($0, 'r+') do |f|
  loop do
    break if f.gets =~ /^__END__/
  end
  f.write(data.to_yaml)
end

__END__
start: 124
end: 127