note
Roy Johnson
Generally, the decision about using <c>?:</c> is not about whether it's necessary, but that capturing whatever you're grouping <i>isn't</i> necessary. The <c>?:</c> modifier makes parentheses not capture, which is somewhat more efficient and might make the task of counting left parentheses less onerous.
<p>
By the way, it's not a lookaround feature.
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