1 2 :D expanded when var set 3 true 4 TRUE 5 :U expanded when var undef 6 true 7 TRUE 8 :D skipped if var undef 9 10 :U skipped when var set 11 is set 12 :? only lhs when value true 13 true 14 TRUE 15 :? only rhs when value false 16 false 17 FALSE 18 do not evaluate or expand :? if discarding 19 is set 20 year=2016 month=04 day=01 21 date=20160401 22 Version=123.456.789 == 123456789 23 Literal=3.4.5 == 3004005 24 We have target specific vars 25 MAN= make.1 26 exit status 0 27