How do I concatenate a string with a value returned from a mule expression?

Question

I am trying something like the following to concatenate a string and a value returned from a mule expression

 <message-properties-transformer scope="session" doc:name="Set value as SessionVar">
        <add-message-property key="someKeyName" value="'Key ' + #[message.inboundProperties['http.query.params']['value']]"/>
  </message-properties-transformer> 

I've tried other variations, as well, without luck. I'll happily post variations, if needed.

Answer 1

Try and use: #['Key ' + message.inboundProperties['http.query.params']['value']]