Perl will not use or require the same file twice without some prodding, so you're not saving anything in your attempted optimization.
Aside from the excellent advice to use Exporter, if your Config.pm file (not a good name BTW) has a package declaration and the variables are package variables, then you can access those variables by their full name (i.e. $Config::foobar) from within your main program and any modules that use your module. It sounds like this is what you're doing, but I wanted to be sure.