found a minor bug, maybe you want to fix it.
I know default values are only useful in combination with global values and therefore "global" is not required. But if I use it then I get an error a001
e.g. this is not working
@startuml
!global $variable = "changed value"
!global $variable ?= "default value"
[A] -> [B]: $variable
@enduml
it is working without global
@startuml
!global $variable = "changed value"
!$variable ?= "default value"
[A] -> [B]: $variable
@enduml
BR Helmut
