I do not agree with Mpolo's suggestion to split this into three tutorials (entitled use strict; use warnings; and use diagnostics;). If you really feel like it needs to be broken up into smaller pages, you should start with a general overview. Then, the second (and possibly third) page(s) could cover the subjects in greater detail. Tutorials are generally geared toward newbies who do not alway benefit from all the details at once (not to say that the details should be skipped). Crawl->Walk->Run kind of thing.
The problem is that use strict is a pain when you first use it a it breaks working code. Hell my sysadmin advised me not to use it! From a new user?s perspective the obvious question is Why do I need to use strict, it breaks my working code?
The tutorial is designed for people without a lot of experience in Perl (i am assuming... since it is a lesson on -w, use diagnostics, and use strict). These are the people that *should* be making sure to include the warnings and diagnostic functions. Even experienced programmers new to Perl should probably enable these functions until they get comfortable with the language.