#!/usr/bin/env perl
use Modern::Perl;

my $lb = 3; # lookback
my $match = qr/\wiz/;
my @buff;

while ($buff[$.%($lb+1)] = ($_ = <DATA>)) {
    my $lbi = ($.+1)%($lb+1); # lookback index
    print $buff[$lbi] if defined $buff[$lbi] and /$match/;
}

__DATA__
foo
bar
baz
biz
buz
goo
car
caz
ciz
cuz