/./ {  # ignore blank lines
  f = "hawk.temp"
  hist[++n] = "prev = " $0
  print "BEGIN {" >f
  for (i = 1; i <= n; i++)
    print hist[i] >f
  if ($0 !~ "=")
    print "print \"   \" prev" >f
  print "}" >f
  close(f)
  system("awk -f " f)
}
