'if' gets ignored

If is not a valid conditional test within a switch statement. If you want to add one, you'll have to do it in the "default" case.

Something like this should work:

when HTTP_REQUEST {
  set uri [string tolower [HTTP::uri]]
  set host [string tolower [HTTP::host]]
  set link "$host$uri"
  switch -exact $link {
    "www.domain.com/1/2/something" {
      HTTP::redirect "http://www.domain.com/something.html"
    }
    "www.domain.com/1/2/something2" {
      HTTP::redirect "http://www.domain.com/something2.html"
    }
    default {
      if { [HTTP::host] equals "www.domain.com" and [HTTP::path] starts_with "/1" } {
        HTTP::redirect "http://www.domain.com"
      }
    }
}

Another way to do this would be without the if by using a wildcard comparison (-glob) in the switch like this:

when HTTP_REQUEST {
  set uri [string tolower [HTTP::uri]]
  set host [string tolower [HTTP::host]]
  set link "$host$uri"
  switch -glob $link {
    "www.domain.com/1/2/something" {
      HTTP::redirect "http://www.domain.com/something.html"
    }
    "www.domain.com/1/2/something2" {
      HTTP::redirect "http://www.domain.com/something2.html"
    }
    "www.domain.com/1*" {
      HTTP::redirect "http://www.domain.com"
    }
}

Hope this helps...