I have following text in a file Message.27.13=%s (%s) value was flatlined in %s for the past %s secondsMessage.27.14=%s (%s) value was flatlined during Pre Market in %s for the past %s secondsI want following text using sed commandMessage.27.13=Regional Email Testing Modification %s (%s) value was flatlined in %s for the past %s secondsMessage.27.14=Regional Email Testing Modification %s (%s) value was flatlined during Pre Market in %s for the past %s secondsBasically, I want to append  = with my custom message which is Regional Email Testing ModificationCan you please help me in solving this. 
Sed command help for pattern mattching and updating same line
sed