AoC 2025 day 3 list version (Perl)

#!/usr/bin/perl

use strict;
use warnings;

use feature         qw(say);

# Change this to 2 for part 1
use constant LEN => 12;

sub chain_index (&@) {
    my $block = shift;
    my $ret = -1;
    foreach my $idx (0 .. $#_ - 1) {
        if (&$block( $_[$idx], $_[$idx+1] )) {
            $ret = $idx;
            last;
        }
    }
    return ($ret);
}

#
# Mainline
#
my @input = map { chomp; [split //] } <>;
my $part2 = 0;

foreach my $bank (@input) {
    my @queue = splice( @$bank, -LEN );

    while (my $jolts = pop @$bank) {
        if ($jolts >= $queue[0]) {
            splice( @queue, (chain_index {$_[0] < $_[1]} @queue), 1 );
            unshift( @queue, $jolts );
        }
    }

    $part2 += join( '', @queue );
}

say "Part 2: $part2";