I had a problem installing Ruby 1.8.5. I got this response from the author of RVM.

From: Wayne E. Seguin wayneeseguin@gmail.com
Date: 12 May 2010 15:01
Subject: Re: Ruby 1.8.5 OpenSSL errors
To: floehopper blah@example.com

Here is the code I had, which is currently commented out in RVM:

How to install ruby 1.8.5... "sneaky sneaky, sir"

src_dir="ruby-1.8.7-p$(rvm_db "ruby_1.8.7_patch_level")"
if [[ ! -d "$HOME/.rvm/src/$src_dir/ext/openssl/" ]] ; then
$rvm_path/bin/rvm fetch 1.8.6-p248 > /dev/null ; fi cp ~/.rvm/src/$src_dir/ext/openssl/extconf.rb
~/.rvm/src/ruby-1.8.5-p231/ext/openssl/ cp ~/.rvm/src/$src_dir/ext/openssl/openssl_missing.*
~/.rvm/src/ruby-1.8.5-p231/ext/openssl/ cp ~/.rvm/src/$src_dir/ext/openssl/ossl_hmac.c
~/.rvm/src/ruby-1.8.5-p231/ext/openssl/ src_dir="ruby-1.8.6-p$(rvm_db "ruby_1.8.6_patch_level")"
if [[ ! -d "$HOME/.rvm/src/$src_dir/ext/openssl/" ]] ; then
$rvm_path/bin/rvm fetch 1.8.6-p383 > /dev/null ; fi cp ~/.rvm/src/$src_dir/ext/readline/* ~/.rvm/src/ruby-1.8.5-p231/ext/readline/
unset src_dir