On Sep 9, 2:44   쮮 
> Anton Ivanov wrote:
>
> >> == Installation
>
> >> % gem install drake
>
> > % gem install drake
> > Successfully installed drake-0.8.1.11.0.1
>
> > % which drake
> > drake not found
>
> % sudo chmod +x /var/lib/gems/1.8/gems/drake-0.8.1.11.0.1/bin/drake
> % /var/lib/gems/1.8/gems/drake-0.8.1.11.0.1/bin/drake -j2
> /var/lib/gems/1.8/gems/drake-0.8.1.11.0.1/bin/drake: invalid option -- j
> % /var/lib/gems/1.8/gems/drake-0.8.1.11.0.1/bin/drake --threads 2
> /var/lib/gems/1.8/gems/drake-0.8.1.11.0.1/bin/drake: unrecognized option
> `--threads'
> --
> Posted viahttp://www.ruby-forum.com/.

It must be pulling the old rake libs.  In all my tests the gem has won
the $LOAD_PATH order.  It is easy to check,

  task :default do
    puts $LOAD_PATH
  end

% rake
/usr/local/stow/ruby-1.8.7-p72/lib/ruby/gems/1.8/gems/rake-0.8.1/bin
/usr/local/stow/ruby-1.8.7-p72/lib/ruby/gems/1.8/gems/rake-0.8.1/lib
[...]

% drake
/usr/local/stow/ruby-1.8.7-p72/lib/ruby/gems/1.8/gems/
drake-0.8.1.11.0.1/bin
/usr/local/stow/ruby-1.8.7-p72/lib/ruby/gems/1.8/gems/
drake-0.8.1.11.0.1/lib
[...]

What does yours say?  Maybe your RUBYLIB environment var is pointing
at a lib directory containing the old rake.rb?