gistfile1.rb

#template containing this
backend appnodes
      <% if @hostname =~ /^s-/ -%>
        option httpchk http://host.subdomain1.company.com/foo.jpg
        server s-app1 1.1.1.1:80 check inter 1m
        server s-app2 2.2.2.2.153:80 check inter 1m
      <% else -%>
        option httpchk http://host.subdomain2.company.com/foo.jpg
        server p-app1 11.11.11.11:80 check inter 1m
        server p-app2 12.12.12.12:80 check inter 1m
      <% end %>

#results in this
backend appnodes
              option httpchk http://host.subdomain1.company.com/foo.jpg
        server s-app1 1.1.1.1:80 check inter 1m
        server s-app2 2.2.2.2:80 check inter 1m