In Routine§

See primary documentation in context for trait is export

multi trait_mod:<is>(Routine $r, :$export!)

Marks a routine as exported to the rest of the world

module Foo {
    sub double($x) is export {
        2 * $x
    }
}
 
import Foo;         # makes sub double available 
say double 21;      # 42 

From inside another file you'd say use Foo; to load a module and import the exported functions.

See Exporting and Selective Importing Modules for more details.

In Mu§

See primary documentation in context for trait is export

multi trait_mod:<is>(Mu:U \type, :$export!)

Marks a type as being exported, that is, available to external users.

my class SomeClass is export { }

A user of a module or class automatically gets all the symbols imported that are marked as is export.

See Exporting and Selective Importing Modules for more details.