Or you could use something other than / for your delimiters, if you're going to have a lot of slashes in your patterns. For instance,

$text =~ s!(.*?)<link=(".*?")>(.*?)</link>!$1<a ref=$2>$3</a>!gi;
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would work. Additionally, there's no need for the first match, so it could just be

$text =~ s!<link=(".*?")>(.*?)</link>!<a ref=$2>$3</a>!gi;
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As for the ?, it is meaningful. *? is a non-greedy match. But in general, I agree with the others that the whole attempt could be an interesting playpen for learning, but really shouldn't be attempted seriously.