Using Ruby on a generic ISP

I wonder how Ruby can be used on a generic ISP right now?

looks like right now i can use a

test.rb in my cgi-bin directory, and it is
not even checking the #!/usr/bin/ruby line

and then i tried a test.erb in the cgi-bin directory or a test.rhtml in
the www directory, and neither of them worked.

the test.erb won’t work with
the line #!/usr/bin/erb or #!/usr/bin/local/erb

So I wonder, can I do something on my own directories so that
test.rhtml, test.erb, ActiveRecord, and ActiveSupport will work?