open OUTFILE, "<$outfile";
open FINAL, ">$final";

while (<OUTFILE>) {
    print FINAL if /(my first line)/;
	print FINAL if /(my second line)/;
	print FINAL if /(my third line)/;

##</code><code>##

line1<br>
line2<br>
line3<br>

##</code><code>##

line 1
line 2

line 3

##</code><code>##

line1<br>
line2<br>
line3<br>