AoC 2023 day 6 (Perl)

#!/usr/bin/perl

use v5.32;
use warnings;

use List::AllUtils  qw(product pairwise);
use POSIX           qw(ceil floor);

sub count_wins {
    my ($t, $d) = @_;

    $d++;
    my $upper = floor(($t + sqrt( $t*$t - 4*$d )) / 2);
    my $lower = ceil (($t - sqrt( $t*$t - 4*$d )) / 2);

    return ($upper - $lower + 1);
}

my @in  = map { [m#(\d+)#g] } <>;
say "Part 1: ", product pairwise { &count_wins($a,$b) } $in[0]->@*, $in[1]->@*;
say "Part 2: ", &count_wins( map { join('', @$_) } @in );