AoC 2024, day 8 (Perl)

#!/usr/bin/perl

use strict;
use warnings;

use feature                     qw(say);

use Math::Vector::Real;
use Algorithm::Combinatorics    qw(combinations);

my %Grid;
my %Antennae;

# Read in grid, make lists of antennae of same frequency
while (<>) {
    chomp;
    my $x = 0;
    foreach my $chr (split //) {
        $Grid{ V($.,++$x) } = $chr;
        push( $Antennae{$chr}->@*, V($.,$x) )  if ($chr ne '.');
    }
}

# Takes a list of harmonics from an antenna to count
sub countAntinodes {
    my %Antinodes;

    foreach my $list (values %Antennae) {
        foreach my $pair (combinations( $list, 2 )) {
            my $delta = $pair->[0] - $pair->[1];

            foreach my $node (map { $pair->[0] + $_ * $delta } @_) {
                $Antinodes{$node}++ if (exists $Grid{$node});
            }
        }
    }

    return (scalar keys %Antinodes);
}

say "Part 1: ", &countAntinodes(1, -2);
say "Part 2: ", &countAntinodes(-$. .. $.);