#!/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