UNIX for Advanced & Expert Users

I'm looking at a config file with dollar signs. What do the dollar signs mean in front of a directory?

Code:

dir = ./demoCA # Where everything is kept
certs = $dir/certs # Where the issued certs are kept
crl_dir = $dir/crl # Where the issued crl are kept
new_certs_dir = $dir/newcerts # default place for new certs.

Config files can be read and used by different kinds programs, not just bash. That config file would fail miserably as a bash script based just on the use of spaces.

It seems to me it means translate (or substitute) the string that is stored in the dir variable - kind of like dereferencing if you will. The author probably figured that $ prepend would improve reading clarity for us UNIX types. Maybe not.