m{
  (?<P>           #    The start of a named capturing block (also $1)

    (?&V)         #      Match a call to the subpattern named <V>

  )               #    The end of the named capturing block

  (?<Q>           #    The start of a named capturing block (also $2)

    .             #      Match any character (except newline)

  )               #    The end of the named capturing block

  (?(DEFINE)      #    The start of a definition block (skipped during matching)

    (?<V>         #      The start of a named capturing block (also $3)

      .           #        Match any character (except newline)

      .           #        Match any character (except newline)

      .           #        Match any character (except newline)

    )             #      The end of the named capturing block

  )               #    The end of definition block
}x