AoC 2024, day 4, part 2 (Perl)

#!/usr/bin/perl

use strict;
use warnings;

use feature         qw(say);

use Math::Vector::Real;

my ($vy,$vx) = Math::Vector::Real->canonical_base(2);
my @Diag = ($vx+$vy, -$vx-$vy, $vx-$vy, -$vx+$vy);

# Read in grid, adding sentinel ~s to right and bottom
my @Grid = map { chomp; y/MS/01/; [split(//), '~'] } <>;
push( @Grid, [('~') x $Grid[0]->@*] );

sub grid_at ($) { my $p = shift; return ($Grid[$p->[0]][$p->[1]]) }

my $part2 = 0;

for (my $y = 0; $y < $#Grid; $y++) {
    SQUARE:
    for (my $x = 0; $x < $#Grid; $x++) {
        my $coord = V($y,$x);
        next SQUARE if (&grid_at($coord) ne 'A');

        my @corners = map {int} grep {/[01]/} map {&grid_at($coord + $_)} @Diag;
        next SQUARE if (@corners < 4);

        $part2 += ($corners[0] ^ $corners[1]) & ($corners[2] ^ $corners[3]);
    }
}

say "Part 2: $part2";