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

[download]

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.

In reply to Re: Printing line before matching expression by jaredor
in thread Printing line before matching expression by rm

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