Short python program that modifies and calls itself.

labrinth.py

import os, subprocess

ITERATIONS = 5

def transform(line):
  return "ITERATIONS = " + str(int(line.split()[2]) - 1) + "\n" if line.startswith("ITERATIONS") else line

with open(os.path.abspath(__file__), "r+") as f:
	new = ''.join(map(transform, f.readlines()))
	f.seek(0)
	f.write(new)

if ITERATIONS > 1:
	print "iterations left: %s" % ITERATIONS
	print subprocess.Popen(["python", os.path.abspath(__file__)], stdout=subprocess.PIPE).communicate()[0],
else:
	print "final iteration!"