C<split_sort> has three required parameters. The first and second paremeters are C<$a> and C<$b> from C<sort> or C<$b> and C<$a> if you want a descending sort. The third parameter is the type of sort you want: C<number>, C<left>, C<right>, or C<alpha> (C<letter>). The fourth parameter is the expression you want to split the strings by and can be ignored for alpha (letter) sort.