installing rubygems as non root

so...install it and it does this?
rdp@ilab4 ~/downloads/rubygems-0.9.4 $ ruby setup.rb --verbose install
rm -f InstalledFiles
---> bin
mkdir -p /home/rdp/i386/bin
install gem /home/rdp/i386/bin/
install gem_mirror /home/rdp/i386/bin/
install gem_server /home/rdp/i386/bin/
install gemlock /home/rdp/i386/bin/
install gemri /home/rdp/i386/bin/
install gemwhich /home/rdp/i386/bin/
install index_gem_repository.rb /home/rdp/i386/bin/
install update_rubygems /home/rdp/i386/bin/
<--- bin
---> lib
mkdir -p /usr/lib/ruby/site_ruby/1.8
install gemconfigure.rb /usr/lib/ruby/site_ruby/1.8/
setup.rb:633:in `initialize': Permission denied - /usr/lib/ruby/site_ruby/1.8/gemconfigure.r b (Errno::EACCES)
from setup.rb:633:in `open'
from setup.rb:633:in `install'
from setup.rb:1377:in `install_files'
from setup.rb:1376:in `each'
from setup.rb:1376:in `install_files'
from setup.rb:1350:in `install_dir_lib'
from setup.rb:1532:in `__send__'
from setup.rb:1532:in `traverse'
... 7 levels...
from setup.rb:826:in `__send__'
from setup.rb:826:in `invoke'
from setup.rb:773:in `invoke'
from setup.rb:1578


try runing ruby setup.rb install --prefix=/path [though it doesn't say this]