The rc.conf file(s) are for -environment variables- only, that are used
by the script in /etc/rc.
The proper place for local shell scripting at startup is /etc/rc.local.
If you -do- ever want to set rc(8) environment variables, consider creating
an /etc/rc.conf.local file.
Please read the FAQ. You'll find a great deal of help within it, especially
suited to questions like yours.