Passing control to another controller In a module I use forms. On special occasions I have to start another form in another module.
In this case I would like to do the following:
1 pass the control from the form to the Controller(1) of the module 
2 this Controller(1) should then pass the control to the Controller(2) of the other module
3 this Controller(2) should start the desired form  

Step 1 and 3 I can perform

Step 2 is still a problem because I read that a controller always must render output.
I do not want to create a new instance of Controller 2 in Controller 1.

Found out that you can return a redirect to another controller. The parameter handling is not yet clear to me, I cannot find a good tutorial about the usage ofRedirect and passing parameters with it.
My aim is the implementation of a Mediator Pattern. Best practice to do this is using the Event Dispatcher Mechanism.
This is explained here.

A good example of implementing the mechanism, even create your own event type (above the existing types of Drupal) is described here