gistfile1.txt

$ perl6 -e 'my $out = shell q|perl6 test.pl6|, :out, :err; say $out.err.lines'
(# subtest 2)

$ perl6 -e 'my $out = shell q|perl6 test.pl6|, :out, :err; say $out.out.lines;'
(# subtest 1     ok 1 - test 1     ok 2 - test 2     1..2 ok 1 - subtest 1     ok 1 - test 3     1..1 ok 2 - subtest 2 1..2)

test.pl6

use Test;

subtest {
    ok 1, "test 1";
    ok 2, "test 2";
}, "subtest 1";

subtest {
    ok 3, "test 3";
}, "subtest 2";

done-testing;