Golf A Parentheses Matching Algorithm
Brain-Flak Classic, 108 bytes

{((((((([][][]){}){}){}()){}){}{}[])()()){{}&lt;&gt;{}(&lt;&gt;)}{}((){[](&lt;{}&gt;)}{}){{}&lt;&gt;[({}&lt;[{}]&gt;)](&lt;&gt;)}{}&lt;&gt;(({}()))&lt;&gt;}


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Stores each opening [ in the right stack, and outputs whenever we hit a ].