When you get a new line onstage, how quickly do you write it down?

The annoying ones are the little accidental lines that get a proper laugh and then vanish from your brain by the time you’re on the train. I try to get the wording into my notes as soon as I’m offstage, before I improve it into something I didn’t actually say. Do you capture the exact line first and decide later whether it belongs in the bit, or wait until you listen back to the recording? I’m much more interested in preserving what happened than trusting my post-gig memory.