Perl for Web Site Management

Warnings via Perl’s -w Switch

Let’s go through the script section by section. First comes the usual top-of-the-script stuff, with one change—the shebang line now has a trailing -w:

#!/usr/local/bin/perl -w

As mentioned in Chapter 2 in the discussion of debugging, -w turns on Perl’s warnings feature, which causes the script to complain to standard error if certain suspicious-looking things appear to be going on. We haven’t bothered with it before this, since the other scripts so far have been so short and simple, but this one is complex enough that it’s worth turning it on.

With that said, you should realize that Perl’s warnings feature is mainly a tool to help you while you’re writing the script. Once the script is written and working properly, there shouldn’t be any warnings.

Tip

Beginning with Perl Version 5.6.0, you can enable warnings by putting a statement that says use warnings; near the beginning of your script instead of using the -w shebang-line switch. If your version of Perl is recent enough to support it, the use warnings approach has some minor advantages over the -w switch, so you should probably use it. In this book I’ll just be using the -w switch.