Passing a variable through an iRule

How can I pass the $domain variable to the portion when CLIENTSSL_CLIENTCERT is running? Most of my work is being done during CLIENTSSL_CLIENTCERT but I would like to import the HTTP::host value.

`when HTTP_REQUEST {
  set domain [HTTP::host]
  }
  when CLIENTSSL_CLIENTCERT {
    set cert [SSL::cert 0]
    set sn [X509::serial_number $cert]
    set subject [X509::subject $cert]
    set issuer [X509::issuer $cert]
    set version [X509::version $cert]
    set clientIP [IP::client_addr]
    log local0. $sn 
    log local0. $issuer
    log local0. $subject
    log local0. $version
    if { [ class match $sn equals $domain ] ||
    [ class match $subject equals $domain ]
    } {
    log $clientIP  
    log local0. "CN and Serial valid" 
    }
    else {
    log $clientIP
    log local0. "cert CN or Serial not valid"
    reject
    }
    }