Exercises and Resources

1. Write a loop that counts from 1 to 100, and
   • Prints out all even numbers
   • Prints out all odd numbers
   • Prints out all the numbers that end in 1, 2, or 7

2. Write a loop that counts down from 100 to 1

3. Write a program that reads standard input and prints out any lines that begin with "hello" in any case (uppercase, lowercase, or mixed case). Hint: look at the "perldoc perlrun" manual page, and try to use Perl's built-in switches instead of writing your own loops.

4. Write a logical condition that will check if a scalar is defined, non-zero, a palindrome (the same backwards and forward), or the number 234.98. Test with and without the warnings "-w" flag to the Perl interpreter and the "use strict" compiler pragma. Do you understand the warnings that were generated, if any?

5. Write the following in normal (non-postfix) notation, and simplify them if you can:

   • print if $debug;
   • $i++ unless $i > 10;
   • unless ($j && !$i) { $j += $i while <> };
   • next while <>;

Resources

• Read the previous chapters of The road to better programming.
  
  
• For related study, take a look at these perldoc pages: perlrun, perlsyn, perlfaq, perlmodlib, strict, and perlop.
  
  
• A good tutorial on logic and Boolean algebra is the "Combinational Logic & Systems Tutorial Guide", by David Belton, April 1998.
  
  
• For the Perl FAQ, refer to http://www.perl.com/pub/v/faqs or http://perlfaq.cpan.org.
  
  
• "Programming Perl Third Edition" by Larry Wall, Tom Christiansen, and Jon Orwant (O'Reilly & Associates, 2000) is the best guide to Perl today, with up-to-date coverage of 5.005 and 5.6.0.
  
  
• Read Teodor's other Perl articles in the developerWorks "Cultured Perl" series:
  • A programmer's Linux-oriented setup
  • Application configuration with Perl
  • Automating UNIX system administration with Perl
  • Debugging Perl with ease
  • The elegance of JAPH
  • Genetic algorithms applied with Perl
  • One-liners 101
  • Parsing with Perl modules
  • Perl 5.6 for C and Java programmers
  • Reading and writing Excel files with Perl
  • Review of Programming Perl, Third Edition
  • Small observations about the big picture
  • Writing Perl programs that speak English
  
  
• Browse more Linux resources on developerWorks.
  
  
• Browse more Open source resources on developerWorks.