Spring loaded parameters...

Physics… meshes… keyboard/text… Thanks to TLL I am completely overwhelmed!

But in the middle of the maelstrom I discover a very, very small but very nice feature of 1.3:

function setup()
    iparameter("clear",0,1)
end

function draw()
    if clear==1 then
    clearOutput()
    clear=0
    end
end

Edit: Added an end at the end.

Cute (add an end to the end)

Nice trick, @Blanchot.