my $adata =   q(athings1 athings2);
my $bdata =   q(bthings1 bthings2);
my $column = 0;
# ...

sort_func($column,$adata,$bdata);

sub sort_func
{
    my ($sortby,$astring,$bstring) = @_;
    # this function uses three arguments.
}

##</code><code>##


if ($sortby eq "string"){
   my $result = sort { $b cmp $a } ($a_items[$item_no], $b_items[$item_no]); 
}
# $result will contain the greater of the two values.

##</code><code>##


    my @a_items  = split("\t", $astring,$limit);
#store the remainder
    my $a_remainder = pop @a_items;

    my @b_items = split("\t", $bstring,$limit);
#discard the remainder
    pop @b_items;