qq (...) quotes everthing between delimiters, but you knew that. Perl is keeping track of the parentheses nesting depth, so there is something like this going on:

$string = qq(           # start the quote
             func(1     # push down to second level
                   ln(  # push down to third level
                      e) # pop up to second level
                  );     # pop up to first level
            );           # finish the quote
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After all, Perl's parser has to do something similar with an equation such as

$a = $b + $c * ($d + $e * ($f + $g * ($h +)));
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