#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11140267
use warnings;

my %answer;
while( <DATA> )
  {
  my (undef, $two, $three) = split /,|\n/;
  $answer{$three}{$two}++;
  }

my $thirty = 1; # FIXME 1 for testing, should be 30

for my $href ( values %answer)
  {
  delete @{$href}{ grep $href->{$_} <= $thirty, keys %$href }
  }
delete @answer{ grep 0 == %{ $answer{$_} }, keys %answer };
$_ = [ keys %$_ ] for values %answer;

use Data::Dump 'dd'; dd \%answer;

__DATA__
702005010683593,5016683593,7020000024140
702005010640383,5016640383,7020000024150
310005010532143,5016532143,7020000034001
702005010637702,5016637702,7020000034001
702005010608274,5016608274,7020000034013
702005010608274,5016608274,7020000034013
310005010609604,5016609604,7020000034013
702005010510869,5016510869,7020000034013
702005010551513,5016551513,7020000034130
702005010551513,5016551513,7020000034130
702005010679719,5016679719,7020000034222
702005010527052,5016527052,7020000034222
702005010645458,5016645458,7020000034222

##</code><code>##

{ "7020000034013" => [5016608274], "7020000034130" => [5016551513] }