rand-api.pl

#!/usr/bin/env perl
use strict;
use warnings;
use feature qw(say);

use if $^O eq 'MSWin32', 'Win32::API';
use if $^O eq 'linux', 'Linux::Perl::getrandom';

my $bytes = int( $ARGV[0] // 8 );
my $buffer = "\0" x $bytes;

if ( $^O eq 'MSWin32' ) {
  my $function = Win32::API::More->new( qw{ bcrypt BCryptGenRandom PPNN N } );
  $function->Call( 0, $buffer, $bytes, 2 );
}
elsif ( $^O eq 'linux' ) {
  Linux::Perl::getrandom->getrandom( buffer => \$buffer );
}

say unpack( 'H*', $buffer );