AoC day 10, Perl, part 2

#!/usr/bin/perl

use strict;
use warnings;

use List::AllUtils  qw(max);

no warnings 'recursion';

my @memo  = (1);
my @adapt = (0, sort { $a <=> $b } <>);

sub recurse_adapt {
    my $idx = shift;

    return ($memo[ $idx ])  if (defined $memo[ $idx ]);

    my $ret = 0;
    my $min = max( $adapt[$idx] - 3, 0 );

    my $i = $idx;
    while( --$i >= 0 && $adapt[$i] >= $min ) {
        $ret += &recurse_adapt( $i );
    }

    @memo[$idx] = $ret;
    return( $ret );
}

print "Part 2: ", &recurse_adapt( $#adapt ), "\n";