The variables can be used to query or logic operation of the current
status of the inputs and outputs. For example, in a 3-sockets with USB
output, the USB output can be switched on when one of the sockets is
switched on:

rule1 on power1#state do event usbpower endon on power2#state do event usbpower endon on power3#state do event usbpower endon
rule2 on event#usbpower do if ( %power1%==1 or %power2%==1 or %power3%==1 ) power4 1 else power4 0 endif endon

or if you want to send a message when the inputs have a defined status:

rule3 on event#test do if ( %switch1%==1 and %switch2%==0 and %switch3%==1 ) publish stat/foo/bar hello endif endon

To use the examples the feature #define USE_EXPRESSION and #define SUPPORT_IF_STATEMENT must compiled in.