#!/usr/bin/perl
open(FILE1, $ARGV[0]) || die "Error: $!\n";
@lines = <FILE1>;

while ($line=<FILE1>){
if ($line=~/^BEGIN_TAG/){
	<FILE1>; #get next line
	if ($line=~/^X1/ .. /^X2/){ # get all between X1 and X2
		
		print $line; # print all of it 
		
	}
}
}

##</code><code>##

BEGIN_TAG
X1 test test test
X2 no no no no
X3 yes yes yes
BEGIN_TAG
X1 test test test
tes test test
X2 no no no no no 
nono non no no
 nononono no no  no
X3 hi hi hi hi hi hi 
hi hi hi hi 
hi hi

##</code><code>##

#!/usr/bin/perl
use strict; 
use warnings;
open (FILE, '<', $ARGV[0]) or die "Could not open file: $!";
my $saveX1=0;
my $saveX2=0;
my $saveX3=0; 
my $savetoX1=''; 
my $savetoX2='';
my $savetoX3='';
while (my $line=<FILE>){
  chomp $line; 
  my @parts=split(' ',$line,2); 
  if ( (!$saveX1) && $parts[0] eq 'X1') { $savetoX1=$parts[1]; $saveX1=1; } 
  elsif ($parts[0] eq 'X2' ||($parts[0] eq 'BEGIN' && $parts[2] eq 'TAG' ) ){ 
       #print $savetoX1."\n" if ($savetoX1) ; 
       $savetoX1=''; 
       $saveX1=0; 
       } 
  elsif ($saveX1) { $savetoX1.=' '.$line; } 

  
  if ( (!$saveX2) && $parts[0] eq 'X2') { $savetoX2=$parts[1]; $saveX2=1; } 
  elsif ($parts[0] eq 'X3' ||($parts[0] eq 'BEGIN' && $parts[2] eq 'TAG' ) ){ 
       #print $savetoX2."\n" if ($savetoX2) ; 
       $savetoX2=''; 
       $saveX2=0; 
       } 
  elsif ($saveX2) { $savetoX2.=' '.$line; } 

  
  if ( (!$saveX3) && $parts[0] eq 'X3') { $savetoX3=$parts[1]; $saveX3=1; } 
  elsif ($parts[0] eq 'BEGIN' && $parts[2] eq 'TAG' ){ 
		#print $savetoX3."\n" if ($savetoX3) ; 
		$savetoX3=''; 
		$saveX3=0; 
       } 
  elsif ($saveX3) { $savetoX3.=' '.$line; } 
  
  
  
  
  }
print "X1: ".$savetoX1."\n" if ($savetoX1) ; 
print "X2: ".$savetoX2."\n" if ($savetoX2) ; 
print "X3: ".$savetoX3."\n" if ($savetoX3) ; 


##</code><code>##


The wrong one (the one I have) I get is: <br/>
<code> X3: yes yes yes BEGIN_TAG X1 test test test tes test test X2 no no no no no  nono non no no  nononono no no  no X3 hi hi hi hi hi hi  hi hi hi hi  hi hi
##</code><code>##

X1: test test test
test test test tes test test
X2: no no no no
no no no no no nono non no no nononono no no  no
X3: yes yes yes
hi hi hi hi hi hi hi hi hi hi hi hi

##</code><code>##

BEGIN_TAG
X1 test test test
X2 no no no no
X3 yes yes yes
BEGIN_TAG
X1 test test test
tes test test
X2 no no no no no 
nono non no no
 nononono no no  no
X3 hi hi hi hi hi hi 
hi hi hi hi 
hi hi