Adding numbers in game states

[James W. <jfc...@ya...>]

Hi all,
 
How does one add a number to a variable? 
For example, here's a state, as defined in Main.lua:
state.blahhumblah=1
 
Now, in a node.lua, I want to do something to this effect:
 
state.blahhumblah=+1
 
So that whenever a function is run it'll increase the state's value by 1. Or subtract it, etc.
 
Anyone know how to do this? It's quite common in other systems, Python, TADS, Inform...
 
Thanks,
  James