"Ken, thanks for your writeup, including forcing me to learn a bit about Test -- I needed that! :-)"

You're welcome. It's good to be able to start a script with use v5.36;.

"I'd rather stick with Perl's slice capability since it reads more cleanly (to me, anyway) ..."

What you choose is entirely up to you. This correlation stood out for me:

"... and doesn't require copying and modifying the source array."

The source array, @test_array, is not modified at all. The temporary copy, @temp_array, is modified in the last statement of (my) get_array_slice_by_python_expr() function; it's then immediately discarded as it goes out of scope.

I added your three new tests, plus a fourth ([:]), to my original code:

    [\@test_array, '[-3:-1]', 'ef'],
    [\@test_array, '[-3:-3]', ''],
    [\@test_array, '[3:-1]',  'def'],
    [\@test_array, '[:]',  'abcdefg'],
[download]

All pass:

1..8
ok 1 - Testing: [:3]
ok 2 - Testing: [:-3]
ok 3 - Testing: [3:]
ok 4 - Testing: [-3:]
ok 5 - Testing: [-3:-1]
ok 6 - Testing: [-3:-3]
ok 7 - Testing: [3:-1]
ok 8 - Testing: [:]
[download]