G'day swampyankee,

"I was expecting ... "SMITH", "-", "JONES" ... I got "S","","M","", ... What did I do wrong?"

The documentation for split describes what happens with capturing. The section at the end (starting with "If the PATTERN contains capturing groups, ...") has a description followed by several examples.

Here's your regex without capturing:

$ perl -E 'say "|$_|" for split /-| /, "A B-C"'
|A|
|B|
|C|
[download]

Now with capturing (and what I think you intended):

$ perl -E 'say "|$_|" for split /(-| )/, "A B-C"'
|A|
| |
|B|
|-|
|C|
[download]

If you coded /(-|)/ instead of /(-| )/, you would get the output you're seeing:

$ perl -E 'say "|$_|" for split /(-|)/, "A B-C"'
|A|
||
| |
||
|B|
|-|
|C|
[download]

That, of course, is just a guess; however, given other issues (already noted by hippo) in your posted code, possibly a good guess.

"The split's documentation seems to say that / / doesn't split between every character, but " " does."

I expect you've misread or misunderstood something. Had you quoted the text that you thought seems to say what you suggest, I could comment further. There can be errors in documentation and those errors can be fixed; perhaps there's not an error but a clarification of the current text would help — obviously, the source of the confusion needs to be identified as a first step.

Anyway, neither / / nor " " will "split between every character":

$ perl -E 'say "|$_|" for split / /, "A B-C"'
|A|
|B-C|

$ perl -E 'say "|$_|" for split " ", "A B-C"'
|A|
|B-C|
[download]

Without the spaces, both will "split between every character":

$ perl -E 'say "|$_|" for split //, "A B-C"'
|A|
| |
|B|
|-|
|C|

$ perl -E 'say "|$_|" for split "", "A B-C"'
|A|
| |
|B|
|-|
|C|
[download]

Regardless, I don't see how / / or " " relate to /(-| )/.