a funny coding challege

[Skaperen]

that's not running itself, it's running a command string.  "itself" means the file, not a command string, and not some other file.  running itself is to run the script file.  if i run the script under python3 then it should run itself under python2, and while running under python2, print "hello", then run itself under python3, and while running under python3, print "world", then do nothing more.  if i run the script under python2 then it should run itself under python3, and while running under python3, print "hello", then run itself under python2, and while running under python2, print "world", then do nothing more.