AoC 2022 day 5 (Perl)

#!/usr/bin/perl

use v5.32;
use warnings;

$/ = '';

# Snarf sections
my @section = map {[split /\n/]} <>;

# grab last line of first section and build (pos -> name) key map for the stacks
my %key;
$_ = pop( $section[0]->@* );
$key{pos() - 1} = $1  while (m#(\w)#g);

# Use rest of section one to build initial stacks
my %stack;
foreach my $line ($section[0]->@*) {
    # Check each position for a crate and stack if found
    foreach my $pos (keys %key) {
        my $crate = substr( $line, $pos, 1 );
        push( $stack{$key{$pos}}->@*, $crate ) if ($crate ne ' ');
    }
}

# Execute commands from second section
foreach my $cmd ($section[1]->@*) {
    my ($num, $src, $dst) = ($cmd =~ m#move (\d+) from (.) to (.)#);

    # Remove reverse for part two:
    unshift( $stack{$dst}->@*, reverse splice( $stack{$src}->@*, 0, $num ) );
}

# First crate from the stacks in the order keys were listed:
say "Part 1: ", map { $stack{$key{$_}}[0] } sort {$a <=> $b} keys %key;