Thank you both for your responses. It appears the text wasn't being replaced due to compression. I changed the irule to include:
when HTTP_REQUEST {
Disable the stream filter for all requests
STREAM::disable
remove the compression offerings from the client
HTTP::header remove "Accept-Encoding"
}
when HTTP_RESPONSE {
Check if response type is text
if {[HTTP::header value Content-Type] contains "text"}{
Replace
STREAM::expression {@Hello@12345@}
Enable the stream filter for this response only
STREAM::enable
}
}
I think the 'overload' function referred to by Michael will come in usefull when we go live.