The variable name is spelled @INC, in uppercase.

Modify it as you would any Perl array: unshift @INC, "some/path";

You need to do this before you actually attempt to load any modules in the new path, so you put it in a BEGIN block:
BEGIN { unshift @INC, "some/path"; }

Or, you can use the lib pragma to do this for you:
use lib "some/path";

Finally, in this case as you mentioned, "." is already in the module search path, so you can do nothing. :-)