Better code check before compile?

[CuriousOne]

Found another.

Here is sample code, both variants should work same, but they don't

if ticker>150 and ard<140 and atrig=0 then
ticker=1 
atrig=1 
endif

This one is fine, but this one:

if ticker>150 and ard<140 and atrig=0 then ticker=1: atrig=1

is not - atrig is always set to 1, no matter if ticker and ard values are as defined in if-then thing. It looks like that code after : is handled as separate code, not part of if-then. But, if I add say GOSUB XX after it, it is executed.