Data group "/" definition

give this a try:

when HTTP_REQUEST {
    if { [string tolower [HTTP::host]] equals "abc.com" && [HTTP::uri] equals "/" } {
        HTTP::redirect "https://def.com"
    }
    elseif { [class match [string tolower [HTTP::uri]] starts_with "/Common/URL_REDIRECT"] } {
        HTTP::redirect "https://def.com"
    }
    else {
        pool POOL_NAME
    }
}