For fun, here's a version that uses a linked list. The "defined" ensures that there is something to be printed. If you change $lookback to 4 and rerun, you'll see it in action.
#!/usr/bin/env perl
use strict;
use warnings;
my $lookback = 3;
my $match = qr/\wiz/;
my @lbuff = map { [] } 1..$lookback;
$lbuff[$_-1][0] = $lbuff[($_) % $lookback] for 1..$lookback;
my $curr = $lbuff[0];
while (<DATA>) {
/$match/ and defined $$curr[1] and print "$$curr[1]";
($$curr[1], $curr) = ($_, $$curr[0]);
}
__DATA__
foo
bar
baz
biz
buz
goo
car
caz
ciz
cuz
P.S. If anyone knows how to reduce the two-line circular linked list definition into one line of idiomatic perl I would love to see it. I'm too tired to think of something clever at the moment.
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