It's not the best idea to place the modules in the same directory as the CGI. Especialy if you use IIS.
Unless you instruct the server to treat .pm special, the modules will be easily downloadable by anyone. It's better to create a private library directory somewhere outside the web root and add
on top of your scripts or to set the PERL5LIB system variable to include that directory.
Under IIS the current directory is NOT the directory where the script is located, but the web root directory. If you insist on placing them alongside the CGI, use