Just trying to see how many '?' I can get in one regex :)

s/,.*?(?:(cd).*?)??,/=$1=/
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This will, of course, give "Use of uninitialized value $1 in concatenation (.)" if you use warnings. Here's a fix for that, if needed.

s;,.*?(?:(cd).*?)??,;=@{[$1 // '']}=;
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or

s/,.*?(?:(cd).*?)??,/$1 ? "=$1=" : "=="/e  # without that @{[]} trick
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