WHO HAS WAKED ME FROM MY SLUMBER?

Oh, it's blazar. Simply put, to do it with regexes, you'd do something like:

my $paren_rx;
$paren_rx = qr{
  \(
  (?:
    (??{ $paren_rx })         # either match another paren-set
    | (?s: [^\\()]+ | \\. )+  # or match non-parens (or escaped parens
+)
  )?
  \)
}x;

my ($chunk) = $string =~ /((??{$paren_rx}))/;
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It's not kid-tested, nor mother-approved, but it feels right, and that's where it counts. In the gut. Long live truthiness. Stephen Colbert++.