Don't access the backreferences from there... save them in a list as a result of the match. (Your way is dangerous if the match fails, by the way.)

use strict;
if (my @matches = /(f.o)(b.r)(b.z)/) {
  print "Match # $_ is $matches[$_-1]\n" for 1..@matches;
}
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-- Randal L. Schwartz, Perl hacker