Paper 0
Pen 100

command MyLine
{
   repeat a 0 100
   {
      repeat b 0 100
      {
         line 0 100 a a
         line a a 100 0
      }
   }
}

command corners
{
   Repeat A 100 0
   {
      Pen A
      Line 0 A A 100}

      Repeat A 0 100
      {
         Pen A
         Line A 0 100 A}
      }

command white
{
pen 0
repeat a 0 10
{
   line 100 (a*a) (a*a) 0
}
}

myline
corners
white