https://github.com/akkartik/mu1/blob/master/fork.mu
 1 # example program: running multiple routines
 2 
 3 def main [
 4   start-running thread2
 5   {
 6     $print 34
 7     loop
 8   }
 9 ]
10 
11 def thread2 [
12   {
13     $print 35
14     loop
15   }
16 ]