The Makefile.PL is just a Perl script, so you can do Perl scripting things in it.

There are some things to consider:

• Remove the cache file on a `make clean` or `make realclean`. In WriteMakefile you can list additional things to remove in the "clean" key.
• Don't leave a file with sensitive information lying around in a build directory.
• You don't have to do everything when you run Makefile.PL. For instance, you can add a MY::test_harness function which will override Makemaker's. In that, you can prompt for a password, then set the enviroment before you call the real test_harness.
• You can also filter files during a `make` with the PL_FILES key in WriteMakefile().

One of our clients is very sensitive about some of the security issues, so we don't test a "live" connection for the module installation. We have another set of script to do that, and they grab the right credentials but do not save them anywhere outside the program. That same script can then be used to verify a set-up later, even when the module distro is gone.

Beyond that, I've had a few requests to add a "config shell" to ConfigReader::Simple, but I haven't had time to do it. Basically, it would load a configuration file then go through it an prompt the user for values. You'd have to start with a config file, but it can be a dummy file.