If the prereq is something that can be found on cpan, then it needs to be listed in the Makefile.PL as one of the "PREREQ_PM => {" items.

However, if it is not a cpan module, you need to ask for this before the Makefile.PL moves on.

Don't test for non perl reqs in your (.t)est files. That will send you fail reports.

You want to ask immediately.

For example, I want to test if 'k3b' cd burning app is installed before I go on..

Makefile.PL

system('which k3b') ==0 
  or die("Missing k3b. Is it installed in this system?");

use ExtUtils::MakeMaker;

WriteMakefile( ......
[download]

Obvioulsy, in the CAVEATS or REQUIREMENTS section of your documentation, let them know what's up.

This will stop that kind of fail report.

(Oops.. Corion's suggestion looks real good compared to my lousy hack!)