The two BEGIN blocks in your second snippet will do the same thing as the three BEGIN blocks in your first snippet, but they are not equivalent.
- Compile first BEGIN block.
- Compile require Test::More;.
- Compile import Test::More;.
- Execute first BEGIN block.
- Execute require Test::More;.
- Execute import Test::More;.
- Compile second BEGIN block.
- Compile use_ok 'Module::A'.
- Execute second BEGIN block.
- Execute use_ok 'Module::A'.
- Compile third BEGIN block.
- Compile use_ok 'Module::B'.
- Execute third BEGIN block.
- Execute use_ok 'Module::B'.
- Compile done_testing;.
- End of compile phase.
- Execute done_testing;.
vs
- Compile first BEGIN block.
- Compile require Test::More;.
- Compile import Test::More;.
- Execute first BEGIN block.
- Execute require Test::More;.
- Execute import Test::More;.
- Compile second BEGIN block.
- Compile use_ok 'Module::A'.
- Compile use_ok 'Module::B'.
- Execute second BEGIN block.
- Execute use_ok 'Module::A'.
- Execute use_ok 'Module::B'.
- Compile done_testing;.
- End of compile phase.
- Execute done_testing;.
Or in short,
- ...
- Compile use_ok 'Module::A'.
- Execute use_ok 'Module::A'.
- Compile use_ok 'Module::B'.
- Execute use_ok 'Module::B'.
- ...
vs
- ...
- Compile use_ok 'Module::A'.
- Compile use_ok 'Module::B'.
- Execute use_ok 'Module::A'.
- Execute use_ok 'Module::B'.
- ...
In the first, use_ok 'Module::A' could have an effect on how use_ok 'Module::B' is compiled. In the second, it can't.
I agree with Corion, though. There's no reason to use use_ok.
use Test::More tests => 1;
use Module::A;
use Module::B;
pass("Loading modules");
1;