On a client's system, where I'd have to run the change management gauntlet to install Text::CSV, I remembered this node. I had to adjust it to handle empty numeric fields (,,,):

$_    = '"",,,"abc",0,,';

print join '|', 
      m/
          "[^"]+"        # quoted string
        | [^,]+          # or non-commas
        | (?<=,)(?=,|$)  # or nothing, surrounded by commas or EOL
       /gx;

# prints:
""|||"abc"|0||
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