if runs code based on a condition

Run a block of code conditionally using if.

if m < 30 
  write "Hello!"

Any number of lines of code can be controlled by if, but it is important to indent the code neatly. Any indented code will only be run if the condition holds true.

else

The opposite condition can be used with else.

if m < 30
  write "Hello!"
else
  write "Goodbye!"

then

If the code for an if is short, it the whole thing can be written on a single line by using the word then after the condition

if f then rt 99 else bk 99