It was first introduced by Why The Lucky Stiff in 2005 with this wonderful haiku:

      "eyes".scan /the_darkness/
catch( :in_the_wind ) { ?a.round; "breath" \
        or "a".slice /of_moon/ }      

greasygreasy followed up with this:

def you are
  false
end

enjoy life while you /can/  

M didn’t want miss the party:

class Starts < AndThenWe
  raise "questions" and require "thought"
end if "we".rjust

U Nakamura came up with a genius one:

$ruby.is_a?(Object){|oriented| language}

Evan Weaver sort of created one:

for desires in heaven do not always end or fade

A silly one I wrote a few years ago:

def initely(awesome, haiku)
 "should".match /your style/ and [:in, :the]
end rescue 007  

Evan Short wrote a bit about falling (not technically a haiku, but I’m not very picky when it comes to awesome code):

#- - - - - - - - - - - - - -#
#                           #
#    a bit about falling    #
#       by: evan            #
#                           #
#- - - - - - - - - - - - - -#

# first of all:
def it_is_ok
#   ok?
          "ok."
end

# but:
#   when a thing
def   hits_the_ground_from the_height
#       if we can assume that the
            remaining_energy = the_height

#   then we can say 
      if remaining_energy
          that_the "thing uses some of the #{remaining_energy} to bounce"
#            and
            rises_to the_next_peak_from(the_height)

      else
#     the thing just
      rests
#     and that is the
      end # of it
end

# it should be noted that:

#    in order to determine the
def    the_next_peak_from the_old_height;
         unless the_old_height < 0.01
#           we assume that
       new_height = the_old_height * 0.5
         else
#          the thing is no longer bouncing
#             percievable to this observer, anyway...
  end
end

# also, 
#    when a thing
#      is dropped
def     from a_height # it 
              hits_the_ground_from a_height
end

# likewise,
#    when a thing
def   rises_to a_new_height
#       then it will fall
          from a_new_height

end

#                 but...
# and most importantly.
#           when the time is just right,
#        the thing just
def          rests;

                  and_we_know it_is_ok

                       #the
                       end

#----------------------------------------------#

                        alias :and_we_know :puts
                        alias :that_the    :puts

herval certainly knows his Shakespear:

question = !!(:to_be or not :to_be)  

smackywentz has a nice description of Rails:

class RubyOnRails
  has_many :features, :through => :bugs
end

Jacques Fuentes has a beautiful letter to his daugther:

require "./love"

a_letter to: Augusta do
  twas(only: 16.months.ago) { The::Universe << You.to(OurFamily) }
  life.has :been => %w(i n c r e d i b l y).zip(*"wonderful!").ever_since
  We::Wish.we_could { experience these_moments: over & over }
  You.will always_be: Loved, and: Cherished
  until Infinity.ends do; Forever.(); end
end

Please let me know if you have another one I can add.