def mSrt([])=[]
addpattern def mSrt([e] as ls)=ls
addpattern def mSrt(ls)=
  print(ls)
  mMrg(mSrt(ls[0:hf]),mSrt(ls[hf:])) where:
    hf=len(ls)//2

def mMrg([],l2)=l2
addpattern def mMrg(l1,[])=l1
addpattern def mMrg(l1,l2 if l1[0]>l2[0])=
  print(l1,'>',l2)
  l1[0:1]+mMrg(l1[1:],l2)
addpattern def mMrg(l1,l2)=
  print(l1,'<',l2)
  l2[0:1]+mMrg(l1,l2[1:])

import random
a=  range(20)|>map$(->random.randint(1,6))|>list
mSrt(a)