No such file to load -- dbi (LoadError)?

Hi,

I'm trying to run a ruby script from the command line (using version
1.8.6 on Fedora linus). But this line:

require 'dbi'

is giving me the error:

[me@mymachine]~/w/easyrx% ruby email.rb
/usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in
`gem_original_require': no such file to load -- dbi (LoadError)
        from /usr/local/lib/ruby/site_ruby/1.8/rubygems/
custom_require.rb:27:in `require'
        from email.rb:8

What do I need to install/configure to overcome this problem?

Thanks, - Dave