http redirect with multiple condetion

I'm assuming you want to send traffic for those 3 hosts to a pool with serverside rewrite and not a clientside redirect (Where URL would be changed and visible to client). So using pool is correct option.

But if traffic for all 3 hosts going to same pool and also there is not other custom requirement for specific host, you can club them together using OR condition. But switch statement would be better.

for last default one you can either use default_pool, reject (reject if host header is coming something diff than defined) or return (to stop processing iRule further and use default assigned pool to vip for other hosts)

when HTTP_REQUEST {
    switch -glob [string tolower [HTTP::host]] {
                "aaaa.com" -
		"bbbb.com" - 
		"cccc.com"	
       {
                HTTP::header replace "Host" "api.com"
		set current_uri [HTTP::uri]
                HTTP::uri "/something$current_uri"
		pool new-pool
       }  
       default {
         return
      }
    } 
 }