Parts of your problem_space is not quite clear to me, so this is largely a shot in the dark. Answers to the questions below will undoubtedly get you better answers.

Are you getting dbname, uname and p/w from something hardcoded in some other part of your script? ... from a form on a webpage? from the CLI?

Any why do want to obtain them within the sub? The reference to using a file sounds as though it might be rooted in a security concern, but that's merely a guess. An appropriate answer will also depend on whether your reference to "the server" is to a web server (Apache, etc) or to a fileserver or something else?

Despite that, taking a stab in the dark, one way to 'get these variables from a file somewhere else on the server" would be to add a block inside the sub (before line 6) opening (and be sure to test the open) the file, and reading the vars.

Why are you using use strict; in the sub. Does that mean you're not using strict (and warnings!) in main? If so, make your life easier by adding both in the head of your script.