sub match {
  local $_ = shift;
      m/  \(([^)]*?)\)  /x    # Both parens.
  ||  m/  \((.*)$       /x    # Left paren.
  ||  m/  ^(.*)\)       /x    # Right paren.
  ||  m/  ^[^()]*()$    /x;   # No parens (no capture).
  return $1 // ();
}