Missed readline on mac os x? [HELP]

I installed ruby 1.8.2 without problem, using the binary provided
on the ruby on rails site for Mac Os X

All works fine, but ruby cannot find the readline library:

[0:Documents/workspace/manhattan> ruby script/console
Loading development environment.
/usr/lib/ruby/1.8/irb/completion.rb:10:in require': No such file to load -- readline (LoadError) from /usr/lib/ruby/1.8/irb/completion.rb:10 from /usr/lib/ruby/1.8/irb/init.rb:218:inrequire’
from /usr/lib/ruby/1.8/irb/init.rb:218:in load_modules' from /usr/lib/ruby/1.8/irb/init.rb:216:ineach’
from /usr/lib/ruby/1.8/irb/init.rb:216:in load_modules' from /usr/lib/ruby/1.8/irb/init.rb:21:insetup’
from /usr/lib/ruby/1.8/irb.rb:54:in `start’
from /usr/bin/irb:13

I have readline5 by fink and I hope it is sufficient (it is located
in /sw/lib)
How can I get ruby find it?
Someone can give me some link or hint to fix the problem?
Thank you!

Plus I remember being impressed with Ada because
you could write an infinite loop without a faked up condition. The idea
being that in Ada the typical infinite loop would normally be
terminated by
detonation. -Larry Wall [ [ [ JJ ] ] ]