AoC 2024, day 5 (Perl)

#!/usr/bin/perl

use strict;
use warnings;

use feature         qw(say);

$/ = '';        # paragrpah mode to split sections
my ($rules, $lists) = map {[split /\n/]} <>;

$; = '|';       # hash key separator set to | (like in the input)
my %order = map { $_ => 1 } @$rules;

my @parts;
foreach my $list (@$lists) {
    my @sorted = sort { $order{$a,$b} ? -1 : 1 } split( /,/, $list );
    $parts[ $list eq join(',', @sorted) ] += $sorted[@sorted / 2];
}

say "Part 1: $parts[1]";
say "Part 2: $parts[0]";