#!/usr/bin/perl -wT
use strict;

my @aoa = ([1,2,3],
           [1,2,3,4,5],
           [1,2,3,4,5,6,7,8],
           [1,2,3,4],
           [1,2,3,4,5,6],
          );

my $i;
my $index = (sort{$$b[1]-$$a[1]}map{[$i++,$#$_]}@aoa)[0]->[0];
print "\$aoa[$index] has the most elements\n";

=OUTPUT
$aoa[2] has the most elements