This worked, thanks--and taught me a couple of things about regular expressions that I'd seen in several of the books but hadn't yet understood.
Still perplexed by the failure of the other regexp. Even
though<kbd> [^,]+ </kbd>does indeed include spaces, I'm perplexed by why
the<kbd> \s* </kbd>preceding and following it fail to catch spaces
when they exist in those locations in the string.<kbd> \s* </kbd>does
catch them when it is used this way:
<kbd>split /\s*,\s*/ , $_</kbd>