=over

=item $<I<digits>> ($1, $2, ...)
X<$1> X<$2> X<$3>

Contains the subpattern from the corresponding set of capturing
parentheses from the last successful pattern match, not counting patterns
matched in nested blocks that have been exited already.  (Mnemonic:
like \digits.)  These variables are all read-only and dynamically
scoped to the current BLOCK.

=back