From mh/docs/mh.txt:

new_second
    new_minute
    new_hour
        These functions are like the $New_Second/Minute/Hour variables,
        except they can return true only on the nth second/minute/hour.

          Examples:

            print_log "This occurs every 10th second" if new_second 10;
            print_log "This occurs once every even hour" if new_second 2;

        If you pass no argument, it defaults to 1 (i.e. the same as the
        $New_* variables).

Regards,
David Satterfield