//#IMPORT(LEGACY|MODERN) to control import semantics.

This is a feature added to help migrate old users from the legacy import semantics.

The special format comment:

//#IMPORT(LEGACY)

means that all following ECL will use the legacy import rules.

//#IMPORT(MODERN)

ensures that it uses the new rules.

The idea is that attributes can gradually be moved over from legacy to modern, but adding
//#IMPORT (MODERN)
to the head of the file, and then fixing any resulting compile issues. Once most attributes are switched over
//#IMPORT(LEGACY)
can be added to any remaining attributes, and the default for the system can be switched from legacy. Any remaining attributes can then be changed as required.

NOTE: Slightly unusually //#IMPORT within a macro definition only applies to the contents of that macro definition. This allows exported macro definitions to be switched over in the same way.