You are running a free Perl programming course? Very interesting. Is the course material somewhere available? I run such a course too in our local computer club and would be interested to exchange views and material. My course is in the Dutch language though.
CountZero
A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James