I now have Ruby 1.8.1 preview2, modruby1.2.2 and Arrow 0.1.0. However 
whenever I restart Apache it says in the log:

mod_ruby:   failed to require arrow
mod_ruby:   error in ruby
mod_ruby:   /etc/arrow/lib/arrow/template/parser.rb:22:in 'require': No 
such file to load -- strscan (LoadError)

etc...etc...etc...

My configuration for Arrow reads:

<IfModule mod_ruby.c>
   RubyAddPath   /etc/arrow/lib
    RubyRequire arrow
    <Location /ruby>
       SetHandler ruby-object
       RubyHandler "Arrow::Dispatcher::instance( '/etc/arrow/demo.cfg' )"
    </Location>
</IfModule>

Any ideas?

Zach