It's not clear what you want to do about spaces around commas. This strips spaces before and after commas:

$data = '1, 2, 3,"a,b,c","d", 4';
@a = $data =~ / *(".*?"|[^,]*?) *(?:,|$)/g;
pop @a;
for (@a) {s/^"(.+?)"$/$1/}
print join "\n", @a;
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