AoC 2024, day 19 (Perl)

#!/usr/bin/perl

use strict;
use warnings;

use feature         qw(say state);
use List::Util      qw(sum);

$| = 1;

# Read sections:
$/ = '';
my @section = map {[split /\n/]} <>;
my @patt = split( /, /, $section[0][0] );

# Part 1
my $patt_re = '^(' . join('|', @patt) . ')*$';
my @good = grep { m#$patt_re# } $section[1]->@*;
say "Part 1: ", scalar @good;

# Part 2
sub recurse_count {
    my ($str) = @_;
    state %memo;

    return ($memo{$str})      if (exists $memo{$str});
    return ($memo{$str} = 1)  if ($str eq '');

    my $ret = 0;
    foreach my $patt (@patt) {
        my $new_str = $str;
        $ret += &recurse_count( $new_str ) if ($new_str =~ s#^$patt##);
    }

    return ($memo{$str} = $ret);
}

say "Part 2: ", sum map {&recurse_count( $_ )} @good;