#!/usr/bin/perl

use strict;
use warnings;

use File::Find;

sub preprocess {
    my %packages;

    foreach (@_) {
        $_ =~ m/^([^_]+)/;
        push @{$packages{$1}}, $_;
    }

    @_ = ();

    foreach ( keys %packages ) {
        my @packages = @{$packages{$_}};
        push @_, (sort @packages)[0 .. scalar @packages - 3];
    }

    return @_;
}

find({
    preprocess => \&preprocess,
    wanted     => sub { print "$File::Find::name\n" }
}, '/var/cache/apt/archives');