Script to extract text from application

I have a Rails application, that has grown quite large. At the moment all texts are placed inside the template files like this:

<h3>This is a header</h3>

And inside the ruby code (like flash messages, model error messages, etc.)

I now have the situation, that I want to place all text in an external textfile in order to be able to e.g. translate the entire site.

Is there an easy way to extract all these texts and replace them with e.g.

l(:some_text_key) in the ruby code and

<%=l(:some_text_key) in the templates?

or do I have to go through all files manually? (yikes)

BTW: I will happily move to Rails 2.2 if that is any help.

- Carsten