use strict;
use warnings;

use List::Util   qw{ shuffle };
use Time::HiRes  qw{ time };

our $N //= 1e3;
our $S //= 1e4;
our $Z //= 5;

my %bools = map { $_ => [] } 1 .. $N;

for my $set ( 1 .. $S )
{
    my $conts = [];
    push @{ $conts }, int rand $N for 0 .. int rand $Z;
    push @{ $bools{ $_ } }, $conts for @{ $conts };
}

my @someOrder = shuffle 1 .. $N;
my $start     = time();

delete @bools{ @someOrder };

printf "Took %.6f\n", time() - $start;