foreach $sub ( @sub_names ) {
    sub $sub {
        #subroutine implementation
    }
}

##</code><code>##

read('light',10); # Retrieve the value of "light" at line 10
read_at_time('light', $timestamp);

##</code><code>##

light(10); # Retrieve the value of "light" at line 10
light_at_time($timestamp);