AoC 2023 day 4 (Perl)

#!/usr/bin/perl

use v5.16;
use warnings;

use List::AllUtils  qw(true sum);

# ASSUME: cards are listed in order
# Array of number of wins for the N+1th card
my @card_wins = map {
                    my @p = split( /[:|]/ );
                    my %win = map { $_ => 1 } split(' ', $p[1]);

                    true { exists $win{$_} } split(' ', $p[2])
                } <>;

# Recursive function: returns number of cards for scratching a card (including self)
my %memo;
sub scratch_card {
    my $num = shift;
    my $ret = 1;

    return ($memo{$num}) if (exists $memo{$num});

    $ret += &scratch_card( $num + $_ ) foreach (1 .. $card_wins[$num]);

    return ($memo{$num} = $ret);
}

say "Part 1: ", sum map { $_ ? 1 << ($_ - 1) : 0 } @card_wins;
say "Part 2: ", sum map { &scratch_card( $_ ) } (0 .. $#card_wins);