The default character set is alpha-numerical based, but can be set to any kind of character list.

The complete handling and generating is implemented in a module, which exports one function: ‘generate_password‘.
This function can take (optional) as arguments:

• a length
• a character list

The entropy is generated with Bytes::Random::Secure and random numbers are generated with Math::Random::ISAAC.

package MORETRIX::Password;
#===============================================================================
#  DESCRIPTION: A password generator module
#     REVISION: $Id: Password.pm 71 2013-07-02 12:28:42Z jmorano $
#===============================================================================

use strict;
use warnings;
use Digest;
use Exporter qw/import/;
use Time::HiRes qw/time/;
use Bytes::Random::Secure;
use Math::Random::ISAAC;

our @EXPORT    = qw/generate_password/;
our @EXPORT_OK = qw/generate_password/;

my $random_state;
my $CHARLIST = q{abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ!"$%&/\()=?{}[]*+#;:.,-_<>|^~'};

# Generate a cryptographic safe random password
# default length: 12
#
sub generate_password {
    my ($length, $charlist) = @_;
    $length   //= 12;
    $charlist //= $CHARLIST;

    my @temp_passwords;
    foreach my $loop ( 0 .. int(random_number(100)) ){
        my $password = '';
        while (length($password) < $length) {
            $password .= substr($charlist, (int(myrand(length($charlist)))), 1);
        }
        push @temp_passwords, $password;
    }

    return $temp_passwords[int(random_number(length(scalar @temp_passwords)))];
}

sub random_number {
    my ($seed) = @_;

    my $r = Math::Random::ISAAC->new($seed);
    return $r->rand();
}

sub mysrand{
    my $seed = shift || (time ^ $ ^ int(random_number(time)) ^ int(random_number(2048 ^ 128)));
    $random_state = {
        digest  => new Digest ("SHA-512"),
        counter => 0,
        waiting => [],
        prev    => $seed
    };
}

sub myrand{
    my $range = shift || 1.0;
    mysrand() unless defined $random_state;

    if (! @{$random_state->{waiting}}){
        $random_state->{digest}->reset();
        $random_state->{digest}->add( generate_entropy(4096) .
                                     $random_state->{counter}++ .
                                     $random_state->{prev});
        $random_state->{prev} = $random_state->{digest}->digest();
        my @ints = unpack("L*", $random_state->{prev}); # 32 bit unsigned integers
        $random_state->{waiting} = \@ints;
    }
    my $int = shift @{$random_state->{waiting}};
    return $range * $int / 2**32;
}

sub generate_entropy {
    my ($length) = @_;

    $length //= 1024;

    my $random = Bytes::Random::Secure->new( NonBlocking => 1, Bits => 4096 );
    return $random->string_from($CHARLIST, $length);
}

1;

Example script:

#!/usr/bin/env perl 

use strict;
use warnings;
use utf8;
use MORETIX::Password;

my $length = shift @ARGV;
$length //= 32;

print generate_password($length) . "\n";
print generate_password($length) . "\n";
print generate_password($length) . "\n";
print generate_password($length) . "\n";
print generate_password($length) . "\n";

References:

• http://wellington.pm.org/archive/200704/randomness/#slide0