ruby paperfolding algorithm

$iterations=2
aArr=[1,1,0]

def fold (arr)
 fArr=arr
 hArr=[]
 j=0
  while j<(fArr.length+1)/2 do
   gArr=[]
   gArr.push(fArr.shift,fArr.shift)

   switch gArr
    when [1,nil]
      hArr.push(1,1,0)
    when [1,1]
      hArr.push(1,1,0,1)
    when [1,0]
      hArr.push(1,1,0,0)
    when [0,1]
      hArr.push(1,0,0,1)
    when [0,0]
      hArr.push(1,0,0,0)
    when [0,nil]
      hArr.push(1,0,0)
    else
      hArr.push("ERROR")
   end
   j+=1
  end

 return hArr.flatten
end

i=1
while i<$iterations do
 aArr=fold(aArr)
 i+=1
end

aArr.each {|x| print x}