Well, first off, using OS based authentication (something like Authen::PAM for Linux) or other mechanisms are much safer idea for restricting access to resources by passwords in scripts. PAM can, for instance, allow you to validate connections based on either who you are running as or possibly what username/password you enter. Lots of other similar tools exist, just search CPAN for Authen. Some monks pointed me this way earlier, and there is a lot of great stuff out there.

If you want to restrict access to a file to keep folks that are not in your group from reading it, do a "man chmod" at the Unix prompt and much of this (but not all) will be explained. "Unix in a Nutshell" or "Unix power tools" (substitute Linux for Unix if you like), or some other sysadmin reference can probably go over permission based security better than I can here. In general, you want read/write/execute access only for owner, or only for owner and group, something like 0770 or 0700 is probably what you want. In the case of an rc file 0660 or 0600.