#!/usr/bin/perl

use strict;
use warnings;

local $/=undef;
my $contents=<DATA>;
my ($thirdline) = $contents =~ m/Line3 : (.*?)\n/s;
print $thirdline."\n";


__DATA__
Line1 : Dit is de eerste regel
Line2 : Dit is de tweede regel
Line3 : Dit is de derde regel
Line4 : Dit is de vierde regel

##</code><code>##

Dit is de derde regel

##</code><code>##

my ($thirdline) = $contents =~ m/Line3 : ([^\n]+)/s;