#! /usr/bin/ruby
ids = {}
ARGV.each do |file|
  File.foreach(file) do |l|
    break if /^$/ =~ l
    if /^Message-Id:\s*<(.*)>/ =~ l
      if old = ids[$1]
        puts "#{file} -> #{old}"
        File.unlink(file)
      else
        ids[$1] = file
      end
      break
    end
  end
end