Chapter 2

This comprises practically all of the universally applicable directions that can 

be given about using modules. In practice, you'll have to at least skim the docu 

mentation for each module you want to use in order to find out how it's meant to 

be used. As you'll see in the following text, there are many, many ways to do it!

Packages

Perl supports modular programming through packages. Packages provide a sep 

arate namespace for variables and subroutines declared inside. This means that 

two packages can have subroutines and variables with the same names without 

inadvertently stepping on each other's toes. You declare a package with a package

statement:

package CGI::SimplerThanThou;

After that, any subroutines or global variables you declare will be in the package. 

For example, this code creates a subroutine param() in the CGI::SimplerThanThou 

package:

package CGI::SimplerThanThou;

sub param {

   return ( fake ,  params );

}

Now if you want to call this subroutine from some other package, you'll need to 

prefix it with the package name:

my @params = CGI::SimplerThanThou::param();

Variables can also be created in a package. Here's an example that creates a 

hash called %params in the CGI::SimplerThanThou package:

package CGI::SimplerThanThou;

%params = ( ten => 10 );

To refer to this variable from another package, you again use the package prefix:

print "Ten: $CGI::SimplerThanThou::params{ten}\n";

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