Encode a Ruby program into a version composed almost entirely of unicode whitespace characters. Decodes itself on the fly.

whitespace-a-like.rb

#!/usr/bin/env ruby
# encoding: utf-8

CHARS = %w{                            ​ ‌ ‍     　}

def encode(string)
  string.chars.map{|c|"#{CHARS[c[0]/16]}#{CHARS[c[0]%16]}"}.join
end

program = <<-EOF
what_to_say = 'Hello World!'
puts "This program will say \\"\#{what_to_say}\\" ten times:"
10.times{puts what_to_say}
EOF

File::open('ciphered.rb', 'w') do |f|
  f.puts "#!/usr/bin/env ruby\n# encoding: utf-8\nh=Hash[%w{                            ​ ‌ ‍     　}.zip((0..15).to_a)]"
  f.puts "eval('#{encode(program)}'.chars.each_slice(3).map{|c|h[c.join]}.each_slice(2).map{|a|((a[0]*16)+a[1]).chr}.join)"
end

# sample output written into ciphered.rb:
#
# #!/usr/bin/env ruby
# # encoding: utf-8
# h=Hash[%w{                            ​ ‌ ‍     　}.zip((0..15).to_a)]
# eval('         　   　 　         ‍         ‌ ‌ 　     　   ‌                                   　       ‍       ‌ ‌           ‌     ​         　   　 　       ‍ ‌                 ‍                     ‍     ​                   　   　 　       ‍  '.chars.each_slice(3).map{|c|h[c.join]}.each_slice(2).map{|a|((a[0]*16)+a[1]).chr}.join)
#
# sample output of running ciphered.rb:
#
# This program will say "Hello World!" ten times:
# Hello World!
# Hello World!
# Hello World!
# Hello World!
# Hello World!
# Hello World!
# Hello World!
# Hello World!
# Hello World!
# Hello World!

Wonderfully useless :)