AoC 2024, day 22 (Perl)

#!/usr/bin/perl

use strict;
use warnings;

use feature         qw(say);
use List::Util      qw(max);

my @input = map { m#(\d+)#g } <>;

my $part1 = 0;
my %hash;

foreach my $num (@input) {
    my @window;
    my %tmp;
    my $last = $num % 10;

    for (my $i = 0; $i < 2000; $i++) {
        $num = (($num <<  6) ^ $num) & 0xffffff;
        $num = (($num >>  5) ^ $num) & 0xffffff;
        $num = (($num << 11) ^ $num) & 0xffffff;

        push( @window, ($num % 10) - $last );
        $last = $num % 10;

        if ($i >= 3) {
            $tmp{"@window"} //= $last;
            shift @window;
        }
    }
    $part1 += $num;
    $hash{$_} += $tmp{$_} foreach (keys %tmp);
}

say "Part 1: $part1";
say "Part 2: ", max values %hash;