thats rule 1, don't roll your own

Which is why I'm posting it here.

no benchmarks

You've got me on this, here's a benchmark. My proposed function is available here. (The repo is outdated, will need to check out devel branch).

#!/usr/bin/env perl

use strict;
use warnings;
use Benchmark qw(cmpthese);
use Dancer::Session::Abstract;
use Apache::Session::Generate::MD5;
use Catalyst::Plugin::Session;
use MVC::Neaf::X::Session;

$SIG{__DIE__} = \&Carp::confess;

my $cat = Catalyst::Plugin::Session->new;

cmpthese( -1, {
    dancer => \&Dancer::Session::Abstract::build_id,
    apache => \&Apache::Session::Generate::MD5::generate,
    catalyst => sub { $cat->generate_session_id },
    neaf => \&MVC::Neaf::X::Session::get_session_id,
});
[download]

Results of its execution on a 0.8 GHz intel laptop:

bash$ perl -Ilib bench.pl 
            Rate   dancer catalyst   apache     neaf
dancer    4886/s       --     -62%     -92%     -93%
catalyst 12922/s     164%       --     -79%     -81%
apache   61265/s    1154%     374%       --     -12%
neaf     69591/s    1324%     439%      14%       --
[download]

no randomness testing

Agreed, will search for a reference for doing that.