Learning Perl, Fourth Edition

Some Important Modules

We describe some of the most important features^[381] of the most important modules^[382] in this section. The modules that we discuss here should be found on every machine that has Perl except where noted otherwise. You can get the latest ones from CPAN.

The CGI and CGI_Lite Modules

Many people use Perl to write programs that a web server will run, called CGI program s. The CGI module comes with Perl, and the CGI_Lite module is available separately from CPAN. We showed an example in Chapter 15, and you can read more in the section "The Common Gateway Interface (CGI)" later in this appendix.

The Cwd Module

Sometimes you need to know what the current working directory’s name is. (You could use ., but maybe you need to save the name so you can change back to this directory later.) The Cwd module, which comes with Perl, provides the cwd function, which you can use to determine the current working directory.

    use Cwd;
     
    my $directory = cwd;

The Fatal Module

If you get tired of writing "or die" after every invocation of open or chdir, then maybe the Fatal module is for you. Tell it which functions to work with, and those will be automatically checked for failure as if you’d written or die and a suitable message after each one. This won’t affect such calls in someone else’s package (code contained within a module you’re using, for example), so don’t use this to fix poorly written code. It’s a timesaver for simple programs in which you don’t need direct control over the error ...