procedure main()
   every 1 to 4 do
   every write(permute("rogram"))
end

procedure permute(s)
   local i, x, t
   if s == "" then return ""
   every i := 1 to *s do {
      x := s[i]
      t := s
      t[i] := ""
      suspend x || permute(t)
      }
end