use strict;
use warnings;

my $csize = 2;   ### Number of lines to save
my (@cache, $str, $c);

my $file = 'data.txt';

open (IN, $file) or die "Can't open $file for read.";
while (<IN>) {
    shift @cache if $#cache == $csize - 1;
    push @cache, $_;
    $c++;

    $str = join '', @cache;
    if ($str =~ /jumped\nover/) {
        print "String found in $file at lines " . ($c - $#cache) . "-$c:\n";
        print $str;
        last;
    }
}

##</code><code>##

the
quick
brown
fox
jumped
over
the
unfortunate
dog

##</code><code>##

String found in data.txt at lines 5-6:
jumped
over