#!/usr/bin/perl use strict; use warnings; use 5.014; my %rand; for (1 .. 2**25) { my $r = rand; $rand{ $r }++; } say scalar keys %rand; use Math::Random::MT::Auto qw(rand); %rand = (); for (1 .. 2**25) { my $r = rand; $rand{ $r }++; } say scalar keys %rand;