Learning Perl, 5th Edition

Exercises

See Appendix A for answers to the following exercises:

1. [15] Rewrite your number guessing program from Exercise 1 in Chapter 10 to use given. How would you handle nonnumeric input? You don’t need to use smart matching.

2. [15] Write a program using given-when that takes a number as its input, then prints “Fizz” if it is divisible by three, “Bin” if it is divisible by five, and “Sausage” if it is divisible by seven. For a number like 15, it should print “Fizz” and “Bin” since 15 is divisible by both 3 and 5. What’s the first number for which your program prints “Fizz Bin Sausage”?

3. [15] Using for-when, write a program that goes through a list of files on the command line and reports if each file is readable, writable, or executable. You don’t need to use smart matching.

4. [20] Using given and smart matching, write a program that reports all the divisors (except 1 and the number itself) of a number you specify on the command line. For instance, for the number 99, your program should report that it is divisible by 3, 9, 11, and 33. If the number is prime (it has no divisors), it should report that the number is prime instead. If the command-line argument is not a number, it should report the error and not try to compute the divisors. Although you could do this with if constructs and with dumb matching, use only smart matching.

   To get you started, here’s a subroutine to return a list of divisors. It tries all of the numbers up to one-half of $number:

   sub divisors { my $number = shift; ...