'.' means the process's current working directory which may or may not be the directory containing the script or the directory containing the module. If you want to make sure you find your modules, use absolute paths.
The whole idea of namespaces (packages) is to avoid accidentally redefining routines and variables when you use a module. When you export names from a module, you have removed this protection barrier. It's better to use @EXPORT_OK and let the user decide which names to import than to use @EXPORT and force it on him.
This isn't such a big deal if you're writing both the module and the program that uses it but if you're writing the module for someone else to use it might become an issue. They may not be aware of all of the names you listed in your @EXPORT array. If one of those names clashes with a name they are already using, they may get unexpected behaviour.
Remember, the user can always get to the routines and variables in the package by specifying the full package name, e.g., $PackageName::PackageVar. Providing it through an export only allows the user to use a shorthand notation.
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