SQL & PL/SQL

I have the function below which will separate comma delimited strings like 1,2,4-7 into
1
2
4-7
and count 3 records:

create or replace function str2tbl
  	 (p_str   in varchar2,
  	  p_delim in varchar2 default ',',
                  p_count out number)
    	 return      myTableType
  as
  	 l_str	    long default p_str || p_delim;
  	 l_n	    number;
	 l_data     myTableType := myTabletype();
   begin
   	 loop
	     l_n := instr( l_str, p_delim );
  	     exit when (nvl(l_n,0) = 0);
	     l_data.extend;
  	     l_data( l_data.count ) := ltrim(rtrim(substr(l_str,1,l_n-1)));
 	     l_str := substr( l_str, l_n+length(p_delim) );
p_count  := p_count +1;

 	 end loop;
 	 return l_data;
 end;

I would like to add the extra functionality so that it would split 4-7 to
4
5
6
7
and return the count on these too like below:
1
2
4
5
6
7
p_count = 6
Any suggestion on how to do it, please?
Thanks