#!/usr/bin/perl
use strict;
use warnings;
use List::Util 'shuffle';

use constant VAL  => 0;
use constant PREV => 1;

my @list = shuffle(1..20);
print "@list\n";
print join " ", Long_Inc_Sub(@list);

sub Long_Inc_Sub {
    my @list = @_;
    my (@pile, @seq);
    NUM:
    for my $num (@list) {
        for (0 .. $#pile) {
            if ($num < $pile[$_][-1][VAL]) {
                my $prev = $_ ? $#{$pile[$_ - 1]} : undef;
                push @{$pile[$_]}, [$num, $prev];
                next NUM;
            }            
        }
        my $prev = @pile ? $#{$pile[-1]} : undef;
        push @pile, [[$num, $prev]];
    }
    my ($prev, $len) = ($#{$pile[-1]}, scalar @pile);   
    while ($len--) {
        $seq[$len] = $pile[$len][$prev][VAL];
        $prev = $pile[$len][$prev][PREV];
    }
    return @seq;
}