learn is special as it is used to create your own commands. The commands you create can take input and return output. Let us take a look at how a new command is created:

learn circle $x {
  repeat 36 {
    forward $x
    turnleft 10
  }
}

The new command is called circle. circle takes one input argument, to set the size of the circle. circle returns no output. The circle command can now be used like a normal command in the rest of the code. See this example:

learn circle $X {
  repeat 36 {
    forward $X 
    turnleft 10 
  }
}

go 200,200 
circle 20

go 300,200 
circle 40  

In the next example, a command with a return value is created.

learn faculty $x {
  $r = 1
  for $i = 1 to $x {
    $r = $r * $i
  }
  return $r
}

print faculty 5

In this example a new command called faculty is created. If the input of this command is 5 then the output is 5*4*3*2*1. By using return the output value is specified and the execution is returned.

Commands can have more than one input. In the next example, a command that draws a rectangle is created:

learn box $x, $y {
  forward $y
  turnright 90
  forward $x
  turnright 90
  forward $y
  turnright 90
  forward $x
  turnright 90
}

Now you can run box 50, 100 and the turtle will draw a rectangle on the canvas.