Get the value of one word dynamically in rails static page cache -

i have static pages in app. app running on 2 different domains.

i want of static pages show <%=@domain%> name. contents static domain name dynamic. how can done in rails?

like

cache  content goes here , want display <%=request.domain()%> end 

with above way: request.domain() cached first , served same domain name ignoring domain using access later.

in view:

<%= request.domain() %> 

on local machine app runs on localhost:3000 above code returns localhost on screen.

cache "first_part_up_to_domain_name"  content goes here , want display  end  <%=request.domain()%>  cache "the_rest_after_domain_name"  rest of content end 

in other cases dynamic pages use expire cache method overwrite cached pages, static pages not sure how can this.