sub sort_func
{
	#local($a, $b) = @_;
	my(@a_items) = split("\t", $a,$datafields);
	my(@b_items) = split("\t", $b, $datafields);
	my($item_no) = $sort;			# the number of the field to 
						# sort on.
	my($result) = 0;			# default is equal
	
	if ($sortby eq "string"){
	    $result = $a_items[$item_no] cmp $b_items[$item_no]; }
	    
	 elsif ($sortby eq "number"){
        $result = $a_items[$item_no] <=> $b_items[$item_no];} 
		return($result);
}