iRule redirect to https if condition doesn't match

You may add the

default

when HTTP_REQUEST {
    switch -glob [HTTP::host][HTTP::uri] {
    "sample1.ehosts.net/word1/word2*" { pool sample1.ehosts.net_word }
    "sample2.ehosts.net/word1/word2*" { pool sample2.ehosts.net_word }
    "sample3.ehosts.net/word1/word2*" { pool sample3.ehosts.net_word }    
    default {     
         add the action here       
    }
   }
}