first.rb

main = "jf*2r112r2"

f1 = "22r"
f2 = "ff*"

f1.gsub!(/2/, f2)
f2.gsub!(/1/, f1)
main.gsub!(/1/, f1)
main.gsub!(/2/, f2)

puts main

puts main == "jf*ff*rff*ff*rff*ff*rff*rff*"

second.rb

class Function
  def initialize
    @instructions = []
  end
  
  def jump
    @instructions << [:jump]
  end
  
  def forward
    @instructions << [:forward]
  end
  
  def light
    @instructions << [:light]
  end
  
  def call(fun)
    @instructions << [:call, fun]
  end
  
  def left
    @instructions << [:left]
  end
  
  def right
    @instructions << [:right]
  end
  
  def execute(funs)
    output = ""
    @instructions.each do |(name,arg)|
      case name
      when :jump
        output << '^'
      when :forward
        output << '+'
      when :light
        output << '*'
      when :call
        output << funs[arg].execute(funs)
      when :left
        output << '<'
      when :right
        output << '>'
      else
        raise "Unknown instruction: #{name.inspect}"
      end
    end
    output
  end
end

def fun(name, &block)
  @funs ||= {}
  f = Function.new
  f.instance_eval(&block)
  @funs[name] = f
end

def run
  @funs[:main].execute(@funs)
end

fun :main do
  jump
  left
  jump
  call 2
  call 2
  call 2
  call 2
end

fun 1 do
end

fun 2 do
  light
  jump
  light
  forward
  light
  jump
  right
end

result = run
expected = "^<^*^*+*^>*^*+*^>*^*+*^>*^*+*"

puts "  Result: " + result
puts "Expected: " + expected
print "          "
result.size.times do |i|
  print((result[i] == expected[i]) ? "." : " ")
end
puts
puts expected == result