Watch

Sorry for being so bland, but how would I use the watch method.
Let’s say I have a variable that becomes true when a key is pressed, and false when it is release. Let’s name the variable key, and the function go. This is my script:

 watch ("key",go) 

.
Should I put anything before watch? If so, what.

Okay, now lets say that function go has a parameter, where. Would the code be like this?:

 watch ("key", go, "NYC")
//or
watch("key", go, ["NYC"]) 

or what?
Thanks for your help.