# Iterate a list
a = [5,6,7,8]
a.each_with_index{ |x, i| puts "#{i} => #{x}" }

# Conditionally end a loop
stop = false
while(!stop) do
  value = rand(5)
  puts "Picked #{value}"
  stop = true if 0 == value
end

# Swap an item in an array with the item before it
a = [1,2,3]
holder = a[2] # think of how you juggle three balls with two hands.
a[2] = a[1]
a[1] = holder
# a is now [1,3,2]