2 :D expanded when var
set
5 :U expanded when var undef
8 :D skipped
if var undef
10 :U skipped when var
set
12 :? only lhs when value true
15 :? only rhs when value false
18 do not evaluate or expand
:?
if discarding
20 year
=2016 month
=04 day
=01
22 Version
=123.456.789 == 123456789
23 Literal
=3.4.5 == 3004005
24 We have target specific vars