examples/perl/t/subtest.t
use strict;
use warnings;

use lib 'lib';
use MyTools;

use Test::More;

is sum(1, 1), 2,  '1+1';

subtest negatives => sub {
    is sum(-1, -1), -2, '-1, -1';
    is sum(-1, -1, -1), -3, '-1, -1, -1';
};

is sum(2, 2), 4,  '2+2';

done_testing;

examples/perl/t/subtest.t.ok
ok 1 - 1+1
    ok 1 - -1, -1
    1..1
ok 2 - negatives
ok 3 - 2+2
1..3
examples/perl/t/subtest.t.nok
ok 1 - 1+1
    ok 1 - -1, -1
    not ok 2 - -1, -1, -1
    #   Failed test '-1, -1, -1'
    #   at t/subtest.t line 13.
    #          got: '-2'
    #     expected: '-3'
    1..2
    # Looks like you failed 1 test of 2.
not ok 2 - negatives
#   Failed test 'negatives'
#   at t/subtest.t line 14.
ok 3 - 2+2
1..3
# Looks like you failed 1 test of 3.

Implicit call to done_testing inside. skip-able, etc.