creating if else structure in puppet templates for more info https://ask.puppetlabs.com/question/288/what-can-i-do-with-erb-templates-in-puppet/

config.erb

    <% if @colo == "a" then -%>
        server server1 foo1.com:8088 check port 8088 inter 5000 rise 2 fall 3 maxconn 5000
        server server2 foo2.com:8088 check port 8088 inter 5000 rise 2 fall 3 maxconn 5000
        server server3 foo3.com:8088 check port 8088 inter 5000 rise 2 fall 3 maxconn 5000
    <% elsif @colo == "b" then -%>
        server server1 foo1.com:8088 check port 8088 inter 5000 rise 2 fall 3 maxconn 5000
        server server2 foo2.com:8088 check port 8088 inter 5000 rise 2 fall 3 maxconn 5000
        server server3 foo3.com:8088 check port 8088 inter 5000 rise 2 fall 3 maxconn 5000
    <% elsif @colo == "c" then -%>
        server server1 foo1.com:8088 check port 8088 inter 5000 rise 2 fall 3 maxconn 5000
        server server2 foo2.com:8088 check port 8088 inter 5000 rise 2 fall 3 maxconn 5000
        server server3 foo3.com:8088 check port 8088 inter 5000 rise 2 fall 3 maxconn 5000
    <% elsif @colo == "d" then -%>
        server server1 foo1.com:8088 check port 8088 inter 5000 rise 2 fall 3 maxconn 5000
        server server2 foo2.com:8088 check port 8088 inter 5000 rise 2 fall 3 maxconn 5000
    <% end -%>