Sorts the LIST and returns the sorted list value.
    If SUBNAME or BLOCK is omitted, "sort"s in stan-
    dard string comparison order.  If SUBNAME is spec-
    ified, it gives the name of a subroutine that
    returns an integer less than, equal to, or greater
    than "0", depending on how the elements of the
    list are to be ordered.  (The "<=>" and "cmp"
    operators are extremely useful in such routines.)
    SUBNAME may be a scalar variable name (unsub-
    scripted), in which case the value provides the
    name of (or a reference to) the actual subroutine
    to use.  In place of a SUBNAME, you can provide a
    BLOCK as an anonymous, in-line sort subroutine.