Structuring repetitions

Often, you need to repeat a block of code lines, either a number of times or while a certain condition holds true. The forever word lets you repeat an unlimited number of times. This should be used with caution—be sure to use break to get out of the infinite loop and continue with the rest of the program. The following snippet shows the life of a fervent book reader:

;-- see Chapter04/repetitions.red:
count: 99
forever [
    print append form count " books to read"
    ; print [form count " books to read"]   ;-- same as append
    count: count - 1
    if count = 0 [break]
]
;== 99 books to read
;...
;== 2 books to read
;== 1 books to read

We break out of the loop when the count down reaches 0.

We use append to join two strings together—the first is form count (which converts count to a string), and the second string is the rest of...