$prompt = "-RN- (-LOC-)";
@user_info = ("juser", "Joe", "3rd floor");

# Here would be some code to do create the sprintf format and
# determine the appropriate array slices
# $patten is determined to be "%s (%s)" and $slices is determined
# to be "1,2";
my $output = sprintf($pattern, @user_info[$slices]);