Errors within Perl Modules

There are two different situations we should be able to handle while using Perl Programming −

• Reporting an error in a module that quotes the module's filename and line number - this is useful when debugging a module, or when you specifically want to raise a module-related, rather than script-related, error.
• Reporting an error within a module that quotes the caller's information so that you can debug the line within the script that caused the error. Errors raised in this fashion are useful to the end-user, because they highlight the error in relation to the calling script's origination line.

The warn and die functions work slightly differently than you would expect when called from within a module. For example, the simple module −

package T;
require Exporter;
@ISA = qw/Exporter/;
@EXPORT = qw/function/;
use Carp;
sub function {
   warn "Error in module!";
}
1;

When called from a script like below −

use T;
function();

It will produce the following result −

Error in module! at T.pm line 9.

This is more or less what you might expected, but not necessarily what you want. From a module programmer's perspective, the information is useful because it helps to point to a bug within the module itself. For an end-user, the information provided is fairly useless, and for all but the hardened programmer, it is completely pointless.

The solution for such problems is the Carp module, which provides a simplified method for reporting errors within modules that return information about the calling script. The Carp module provides four functions: carp, cluck, croak, and confess.