AoC 2025, day 6 part 2 (Perl)

#!/usr/bin/perl

use strict;
use warnings;

use feature         qw(say);
use List::Util      qw(sum product zip);

sub chain (&@) {
    my $block = shift;
    return (map { &$block( $_[$_-1], $_[$_] ) } (1 .. $#_));
}

# Read input:
my @input = <>;
my @ops   = map { split /\s+/ } pop @input;

# Find space delimiters (those shared by all lines)
my %spaces;
foreach (@input) {
    $spaces{pos($_)}++ while (m/\s/g);
}

my @spaces = sort {$a<=>$b} grep { $spaces{$_} == @input } keys %spaces;

# Do calculation:
my $part2 = 0;
foreach my $width (chain {$_[1] - $_[0]} (0, @spaces)) {
    # Grab next numbers with the trailing space delimiter
    my @horz = map { [split //, substr( $_, 0, $width, '' )] } @input;
    my @vert = grep { m#\d# } map { join( '', @$_ ) } zip @horz;

    $part2 += (shift @ops eq '+') ? sum @vert : product @vert;
}

say "Part 2: $part2";