=over

=item @-

$-[0] is the offset of the start of the last successful match.
C<$-[>I<n>C<]> is the offset of the start of the substring matched by
I<n>-th subpattern, or undef if the subpattern did not match.

Thus after a match against $_, $& coincides with C<substr $_, $-[0],
$+[0] - $-[0]>.  Similarly, C<$>I<n> coincides with C<substr $_, $-[>I<n>C<],
$+[>I<n>C<] - $-[>I<n>C<]> if C<$-[>I<n>C<]> is defined, and $+ coincides with
C<substr $_, $-[$#-], $+[$#-]>.  One can use C<$#-> to find the last
matched subgroup in the last successful match.  Contrast with
C<$#+>, the number of subgroups in the regular expression.  Compare
with C<@+>.

This array holds the offsets of the beginnings of the last
successful submatches in the currently active dynamic scope.
C<$-[0]> is the offset into the string of the beginning of the
entire match.  The I<n>th element of this array holds the offset
of the I<n>th submatch, so C<$+[1]> is the offset where $1
begins, C<$+[2]> the offset where $2 begins, and so on.
You can use C<$#-> to determine how many subgroups were in the
last successful match.  Compare with the C<@+> variable.

After a match against some variable $var:

=over 5

=item C<$`> is the same as C<substr($var, 0, $-[0]>)

=item C<$&> is the same as C<substr($var, $-[0], $+[0] - $-[0]>) 

=item C<$'> is the same as C<substr($var, $+[0]>)

=item C<$1> is the same as C<substr($var, $-[1], $+[1] - $-[1])>  

=item C<$2> is the same as C<substr($var, $-[2], $+[2] - $-[2])>

=item C<$3> is the same as C<substr $var, $-[3], $+[3] - $-[3]>) 

=back

=back