Problem

test.pl produces

test, successfully wrapped
a

test2.pl produces

Cannot invoke this object (REPR: Null; VMNull)
  in block  at (...)testimport.pm (testimport) line 7
  in any enter at gen/moar/m-Metamodel.nqp line 4012
  in block <unit> at test2.pl line 6
  
Unfortunately I am at a loss as to why.

test.pl

#!/usr/bin/env perl6

use v6;

multi sub trait_mod:<is>(Routine:D $r, :$wrapped!) {
    $r.wrap: -> |args {
        put "test, successfully wrapped";
        callsame
    }
}

sub test(Str $a) is wrapped {
    $a.say
}

test("a");

test2.pl

#!/usr/bin/env perl6

use v6;
use testimport;

test("a");

testimport.pm

#!/usr/bin/env perl6

unit module testimport;

multi sub trait_mod:<is>(Routine:D $r, :$wrapped!) {
    $r.wrap: -> |args {
        put "test, successfully wrapped";
        callsame
    }
}

sub test(Str $a) is wrapped is export {
    $a.say
}