Unless I misunderstand the question you could use the %INC hash to find out where acme.pm was loaded from.

For example

use lib "lib/products";
use CTtools;
print "$INC{'CTtools.pm'}\n";
[download]

prints "lib/products/CTtools.pm".

This should let you find the directory where "acme.pm" is found, and thus the config file.

Michael